Applied Ergonomics 50 (2015) 8e18

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Applied Ergonomics journal homepage: www.elsevier.com/locate/apergo

Practicing universal design to actual hand tool design process Kai-Chieh Lin a, Chih-Fu Wu b, * a b

The Graduate Institute of Design Science, Tatung University, Taipei, Taiwan Department of Industrial Design, Tatung University, Taipei, Taiwan

a r t i c l e i n f o

a b s t r a c t

Article history: Received 25 March 2014 Accepted 16 December 2014 Available online

UD evaluation principles are difficult to implement in product design. This study proposes a methodology for implementing UD in the design process through user participation. The original UD principles and user experience are used to develop the evaluation items. Difference of product types was considered. Factor analysis and Quantification theory type I were used to eliminate considered inappropriate evaluation items and to examine the relationship between evaluation items and product design factors. Product design specifications were established for verification. The results showed that converting user evaluation into crucial design verification factors by the generalized evaluation scale based on product attributes as well as the design factors applications in product design can improve users' UD evaluation. The design process of this study is expected to contribute to user-centered UD application. © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Keywords: User participation Product design process Universal design (UD)

1. Introduction The term universal design (UD) was proposed by the American architect Ronald L. Mace in 1985 during the development era of “barrier-free design” (Kawauchi, 2001). The purpose of UD is to promote interaction between products and the environment, and to allow users to use the product effectively without having to adjust to the product (Connell et al., 1997). The concept of universal design is making mainstream products and services accessible for whom mainstream users and those with specific requirements without special adaptations (Keates and Clarkson, 2003). After North Carolina State University established the Center of Universal Design (CUD), its research teams formulated seven UD principles (Connell et al., 1997). Subsequently, Satoshi Nakagawa considered the economic, aesthetic, and environmental friendliness dimensions, and added three supplemental dimensions: durability and economics, quality and aesthetics, and health and environment (Nakagawa, 2006). This enabled designs to increase their interaction with users. Comparatively, the 3B principles proposed by Ronald L. Mace (better design, more beautiful, and good business; Mace, 1970) focused on the economic and aesthetics dimensions, but were overly abstract when used in actual applications. Therefore, in consideration of practical applications, the Japan

* Corresponding author. No. 40, Sec. 3, Zhongshan N. Rd., Zhongshan Dist., Taipei City 104, Taiwan. Tel.: þ886 917 018 617. E-mail address: [email protected] (C.-F. Wu). http://dx.doi.org/10.1016/j.apergo.2014.12.008 0003-6870/© 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Ergonomics Society employed equitable use as the basic principle and the three product dimensions of operability, functionality, and attractiveness to compile UD principles (Japan Ergonomics Society, 2007). The results indicated that the principles and context of UD evolved over time, and varied according to different requirements in various industries. Japanese industries have attempted to implement UD in actual applications. To facilitate the development of UD, Mitsubishi Electric built the UD-Checker UD evaluation tool (Sawada et al., 2006). Toyota applied UD thinking to conduct evaluations of the ergo-index and scene conformity level (Kanamori and Misugi, 2004). This indicates that the UD product market based on the “respect each individual to achieve selfactualization” ideal is rapidly growing. User requirements, market knowledge, and approaches that are easy to understand are used to design and produce products that can achieve maximal usability for individual users. However, in the nearly 30 years of implementation since Ron Mace proposed the term UD in 1985, industries still lack sufficient design-related knowledge to realize UD (Vanderheiden and Tobias, 2000). Actual applications typically involved the use of UD scales (“scales useable for everything”) for conducting postevent product evaluations. There are several specific modules were developed to modify products so that could become universal has been brought up as strategies for universal design (Clarkson et al., 2003; Moon and McAdams, 2009). Based on target user simulation and product evaluation, University of Cambridge attempted to practice the idea of universal design into product design process (Clarkson, 2008; Clarkson et al., 2003, 2008; Langdon et al., 2008a,b; Waller et al., 2008). The research team

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integrated user trials to identifying usability problems and exclusion calculation, an expert appraisal method based on demographic population estimated how proportion of the people would be excluded from universal evaluation of products and services due to lack of capabilities or limitations (Keates and Clarkson, 2003; Waller et al., 2009, 2010). It was recommended to use both methods meanwhile to provide different guidance needed which were identifying behavior capability problems or needs by exclusion calculation and were expecting unexpected user behavior and cognition (Clarkson et al., 2007; Goodman-Deane et al., 2014). However, it is hard to identify the user group and find out who the boundary user are. Besides, for the universal design tool of exclusion calculation, it is difficult to define who the expert is to evaluate vision, hearing, thinking, dexterity, reach & stretch and locomotion (Goodman-Deane et al., 2014). In the other hand, in the perspective of design practice in past researches, marketing, economy, feasibility and its evaluation with respect to disabilities and limitations were considered to develop a method and make decisions for universal product families' design (Moon and McAdams, 2009). The product platform was established by mathematical method of Bayesian Game to identify the best module of product families regarding uncertainly market environments (Moon and McAdams, 2010). Kostovich et al. integrated the activity diagram, a progression to examining user interaction from purchase to recycling or disposal of products (Otto and Wood, 2001), and functional model, a graphical illustration of product functionality (Hirtz et al., 2002; Otto and Wood, 2001), to create a product analysis framework which was called actionefunction diagram (Kostovich et al., 2009). The diagram based on the concept of graphical representation during the early stages of design, a single graphical representation of user activity and product function which thus made user centric thinking and information available. According to the differences within functionality, morphological and parametric, products were categorized into universal one and its typical counterpart and the comparisons were applied to each pair afterward in order to analyze and practice into the researches of universal design (McAdams and Kostovich, 2011). Furthermore, universal architectural systems and consumer products were compared formally at the function level (Sangelkar and McAdams, 2010); and the transferability of application from American with Disabilities Act (ADA) to universal design of consumer products was detailedly analyzed (Sangelkar and McAdams, 2012). However, managing differences in product attributes by using scale designs is difficult, and scale evaluations are typically conducted during product design or after mass production is completed. In addition, design teams often make speculations and decisions based on their own experiences, intuitions, and assertions (Mitsufuji and Uchida, 1993). Even if the design team is experienced and possesses accurate intuition, the team cannot accurately convert user evaluation data into design factors without establishing reliable information for evaluating design factors (Haapalainen et al., 1999/2000). In a situation where user evaluations cannot be converted into design factors, the team can expect the future product to have only certain functions, but cannot propose product attribute design factors that conform to the spirit of UD. Therefore, a product design perspective was used in this study to propose a UD application methodology, which is expected to contribute to UD application in product design. Although industries generally use automated machines and automated production in contemporary product design, hand tools are still the primary and most direct contact medium for workers (Christensen and Bishu, 2000). Additionally, “do it yourself” (DIY) trends were used in this study to explore actual self-actualization ideals. Previous related studies have focused on the design product of using a tool in itself, and explored the quality of the design by using task-

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orientated results. In recent years, design thinking has extended to the work-place environment, and whether users can easily and comfortably implement work tasks has been investigated (Aptel et al., 2002; Marsot and Claudon, 2004). Because comfort in operating a product influences the purchase intentions of consumers, comfort is a factor that manufacturers have wished to explore (Vink et al., 2005). Feelings of discomfort can reduce users' operating performance and work satisfaction (Fellows and Freivalds, 1991). Numerous scholars have indicated that comfort and users' work performance are directly linked (Kuijt-Evers et al., 2006; Dempsey et al., 2002). Therefore, comfort is a factor that cannot be overlooked in hand-tool design. However, product attributes of hand tools differ greatly, and the overall value of exploring similar design factors is not high. Therefore, needle-nose pliers were used in this study as an example because many people use this product in daily life, and because needle-nose pliers have clear design factors. End users were invited to participate in the design process. In addition, this study focused on the following four aspects during the exploration of UD application in the product design model: 1) the context of UD which evolves with time; 2) development of an appropriate generalized evaluation scale based on product attributes; 3) examination of the importance of universal product design factors in conducting design verification; and 4) the proposal of new UD principles. 2. Research method and procedure Research method and procedure are divided into four sections from discussing the changed in the context of UD and its evaluation scale. The concept and development of UD are dynamic and the scale may be varied by product types. Third, most of the past UD application researches belong to postevent evaluation instead of initial design process. At last, the new UD principle is proposed over time and with changes in user requirements. Needle-nose pliers were used as an example, and end users were invited to participate in the design. This study was not limited to design evaluations, and user evaluations and opinions were converted into design factors to implement UD in the product design process. 2.1. Changes in the context of universal design UD has been recognized as the current design trend around world. In the past 30 years of UD development, numerous scholars and organizations have proposed theories and insights that enable people to understand UD concepts. The Japanese scholar, Naoaki Nippashi, proposed the “design for ourselves” concept in 2006. Nippashi investigated the implementation of UD in practical applications, how UD will be expressed in the future (Nippashi et al., 2006). The scope of UD thinking is broad and diverse, but a method for practical application has not been proposed. The seven principles proposed by Satoshi Nakagawa, Ron Mace, and the Japan Ergonomics Society, and the supplemental principles of economics, aesthetics, and environmental friendliness reflect design and practical requirements, which increase the comprehensiveness of UD principles. This indicates that the context of UD will change over time and with changes in practical requirements. 2.2. The development of generalized evaluation scales Comfort is a major factor that influences hand-tool design and use. However, the context of UD includes broad practical values, and comfort is only one part. Comfort alone cannot provide users with maximal benefit. UD concepts and comfort factors related to hand tools were used to conduct the research in this study. Based on the development and application of existing UD principles, 10

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UD-related concepts were investigated in this study: UD principles proposed by Mace, application and implementation of UD in Japan, design for ourselves, inclusive design, user centered design (UCD), user experience design (UED), emotional design, human interface, ecodesign, and lifestyles of health and sustainability (LOHAS). These principles were used to compile 71 UD-related words (Nippashi et al., 2006). Additionally, the method used by Dutch scholars Kuijt-Evers et al. for evaluating hand-tool usability was employed to extract 36 words related to comfort, and introduce four vocabulary items that are highly correlated with comfort (professional looks, styling, nice color, and solid design; Zhang et al., 1996). In addition, words related to items that influence user experience were extracted from the feedback of users provided during qualitative questionnaire interviews (factors that influence the purchase of needle-nose pliers and user experience). These extracted words were used to build a UD word database and compile 118 representative words related to hand-tool evaluation (Kuijt-Evers et al., 2004). Furthermore, specialized words were avoided to reduce cognitive differences and misunderstandings among users. The evaluation items used in this study were compared and compiled using contemporary UD principles and evaluation items. Evaluation items were defined individually by considering the relationship between target product attributes and UD words. Item analysis was used to evaluate the relevance of the pretest items, the reliability of individual scale items, and the suitability of the overall scale. Factor analysis was used to eliminate items that were inappropriate or had a weak relationship with the target product. A new generalized evaluation scale was constructed according to the dimensions covered by each product attribute. 2.3. Relationship between UD evaluation items and design factors Evaluation scales are generally used on products or things for conducting user evaluations in UD or other fields of academic research. The resulting scores are used to determine the quality of the product or item. However, evaluation results alone cannot be used to convert user opinions into design factors directly. If the evaluation scale enables users to conduct evaluations, but does not enable designers to understand the implications of the evaluation results, then designers can rely only on subjective opinions, repeated tests, and simulations to achieve product modification or innovation in subsequent development processes. This enables designers to understand clearly the importance of user opinions and evaluation feedback derived from the scale evaluation, and facilitates the improvement of their designs. The results of this study are expected to serve as a reference for designers in the future design of needle-nose pliers that include UD. 2.4. New UD principles The context and development of UD change over time and with changes in user requirements. Factor analysis was used to effectively compile generalized evaluation items into new UD principles. Although the number of extracted factors was not high, a large amount of explained variance is required. The difference in the items comprising the common factors was small, which enabled the convenient naming of factors. In addition, the items comprising the factors were appropriate, which confirmed the construct validity of the new UD principles. To confirm the reliability and validity of the scale further, the Cronbach's a coefficient obtained from the reliability analysis was used as the standard (Bryman and Cramer, 1997) to judge the stability and reliability of each principle in the scale, and confirm the authenticity of the scale items and principles.

3. Experimental procedures A relational investigation based on the UD words obtained in the literature review, the characteristics of needle-nose plier use, and design factors was conducted to identify appropriate words for use in the generalized needle-nose plier design evaluation scale. Cluster analysis was used to select representative test samples based on design characteristics. Participants were invited to conduct the evaluation of the new UD scale by operating representative test samples. Item analysis was used to eliminate inappropriate evaluation items, and principle component analysis was used to group evaluation items, obtain UD principles, and compile a generalized needle-nose plier design evaluation scale. Finally, quantification theory type I was used to examine the relationship between the evaluation items and design factors based on the obtained design principles and product-design factors to clearly convert user evaluations and preferences into design factors, and to provide standards for design verification. This was divided into the following three parts (Fig. 1). 3.1. Participants In accordance with the UD ideal of suitability for most people, and considering experiment safety and user experience, the participants selected for this experiment were healthy people over 12 years of age. Human physiological functions begin to degrade at the age of 40 years. At 65 years, people's vision and organ functions begin to degrade, and analytical, judgment, and calculation abilities gradually degrade to 75e80% of the original ability (Morimoto et al., 2001). People's response ability also decreases with age. When encountering complex situations, degradations in cognitive function can influence decision making in elderly people (Salthouse, 1992). However, in situations in which a person has accumulated years of user experience involving a single mental task, elderly people possess superior operating skills compared with those of young people (Charness, 1981). Based on the aforementioned cutoff point, the target group for this experiment was people between 12 and 65 years of age, with 10 years as the delineation between each age group. Sex was another considered factor. Because of differences in the target product's attributes, male users outnumbered female users. Additionally, previous research exploring hand-tool user comfort indicates no significant difference in the needs of DIY users compared to professional users, and, therefore, they can be perceived as one group (Kuijt-Evers et al., 2004). Therefore, random sampling was used in this study to allocate professional users and typical household DIY users proportionally to the various study groups to implement the essence of UD. From a UD qualitative research perspective, the broader the age group distribution, the better can the importance and equitable use in society of individuals in different age groups be highlighted. The difference in the ratio of men to women indicates that the male participants outnumbered the female respondents because the female respondents lacked hand-tool user experience. The participant demographics are shown in the following table (Table 1). 3.2. Work tasks Work tasks that facilitate user operation and evaluation were established to enable participants to express their feelings and opinions accurately during the product evaluation. Evaluations were conducted using the same operation experience standards. Qualitative questionnaires and partially close-ended questions were used to interview the participants regarding work tasks that require needle-nose pliers. The results indicate that most people

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Fig. 1. Research structure.

use needle-nose pliers for “clamping with the tip,” “fixing,” “cutting,” and “bending” tasks. Because most people use needle-nose pliers to perform these four common tasks, these tasks were used as the work tasks for this experiment. 3.3. Representative test samples The selected target product must be a mature product with clearly defined design factors. Unclearly defined design factors can Table 1 Study participant demographics. Male Female Age range Average Standard age deviation (SD) Representative test samples 18 Generalized needle-nose plier 23 design evaluation scale Design verification 3

10 16

15e65 16e65

34.3 39.5

13.6 15.3

7

23e65

40.8

14.9

cause cognitive confusion and the inability to implement user evaluation findings during the design stage. Products that are still in the development stage or have newly introduced functions have unclear product design factors, and the use of these products can result in inadequate experimental samples. Using different methods to operate products with dissimilar attributes can produce few overall benefits of applying common factors. Therefore, a single-attribute tool (the needle-nose plier) was selected as the target product in this study. Based on market segmentation and differences in exterior styling, function, brand, and place of origin, a total of 33 needle-nose pliers on the market were collected. To prevent an excessive number of samples from influencing the mental workload of the participants, a qualitative user experience questionnaire in which a 7-point Likert scale was implemented was used to explore the factors that influence the user purchase of hand tools. The results were transformed into hand-tool evaluation attributes (aesthetics, convenience, and operability). These attributes and the “comfort” described in hand-tool-related research were

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used as evaluation factors. Cluster analysis was used to compile the target product's design characteristics. User perspectives were used to examine needle-nose plier design factors and select representative test samples. Prior to distributing the questionnaires to the participants, the design factors that influence needle-nose pliers and the procedures used in this experiment were explained to the participants. The needle-nose plier components were defined as the plier head and handles. The overall design considerations for the plier head included a head with or without serration, a wire stripper, and a wire cutter. The design considerations for the plier handle included the material, textured handles, degree of styling changes, and a springback design (springs or a spring plate). The size and weight of the overall product were factors that influenced the needle-nose plier evaluation (Fig. 2). To convert user opinions into design factors, literature reviews and discussions with experts were conducted to define the needlenose plier design factors clearly and provide the participants with the same evaluation standards. The definitions of the needle-nose plier design factors used in this study are shown in Table 2. 4. Results and discussion 4.1. Representative test samples Cluster analysis was used to obtain representative test samples. Various needle-nose plier design factors were considered, and representative samples in the cluster groupings were selected based on design factors to ensure that the selected samples represented design factors. The needle-nose pliers were divided into nine groups based on cluster analysis dendrogram groupings and the influence of mental workload in the subsequent research experiment. Representative test samples were randomly selected from each group's random number table and are shown in Table 3. 4.2. New UD evaluation scale Words in the UD word database compiled for this study that had similar semantics or repeated meanings, and that could easily cause confusion in the participants, were merged. A none one-to-one scale item design was used. Specialized terms were rewritten as understandable descriptions to enable people from various backgrounds to understand the descriptive semantics. Comparisons were made using existing scale evaluation items, and 82 evaluation items were compiled and obtained for this study. Because product

Table 2 Needle-nose plier design factors. Needle-nose plier design factors

Springback design Serrated plier head Plier handle Material Textured handle design Styling change Overall length

Type Level 1

Level 2

Level 3

Springs Yes Single Yes Simple Short 12e14 cm

Spring plate No Composite No Average Medium 14e16 cm

None e e e Complex Long 16e17 cm

attributes may be incompatible with previous user experience, knowledge, and product semantics, a relational investigation was conducted. This process produced 66 evaluation items for the new UD evaluation scale. To understand participants' cognition level toward UD, which was reflected in their evaluation of the representative test samples, and considering that participant preferences toward the samples could influence the evaluation, overall evaluation items (“Do you think this product conforms to UD concepts” and “Your level of preference toward this product”) were added to obtain the new UD evaluation scale. 4.3. Universal needle-nose plier design factors This study introduced UD concepts into initial product design to establish the product design process. Using needle-nose pliers as examples, this study is expected to provide overall recommendations for universal needle-nose plier design based on the overall evaluation item of “do you think this product conforms to UD concepts.” Based on the evaluation of this item, quantification theory type I was applied to the overall UD evaluation to reflect user UD perspectives on the design factors of needle-nose pliers directly. Quantification theory type I is used for determining the relationship between design factors and evaluation items. The results can provide references and considerations for designers and manufacturers in developing future needle-nose plier designs, and the developed process can be applied to other types of products. The partial correlation coefficient in Table 4 indicates that the springback design was the primary design factor that influenced the evaluation of universal needle-nose pliers. Other crucial factors were length and degree of styling change in the plier handles. Optimal design factors (spring plate, non-serrated plier head, single-material plier handle, non-textured handle design, average styling change, and medium length) were obtained using the type scores. 4.4. New UD principles

Fig. 2. Needle-nose plier design characteristics.

The new generalized evaluation scale was extracted using principle component analysis, which was based on each item's weighted importance. UD principles were formed by eliminating or reordering each evaluation item, and were based on each principle's influence and importance during the design process and product use. Seven main components, functionality (F1), selfactualization (F2), aesthetic and commercial value (F3), level of work achievement (F4), space and environment (F5), accommodation (F6), and adjustability (F7), were obtained. An accumulated explanatory rate of 0.5 was used as the judgment standard (Field, 2000) to obtain 42 subevaluation items as shown in Table 5. The seven main components were not completely independent, and relationships and continuity existed among them. The Cronbach's a coefficient obtained from the reliability analysis was used as the judgment standard to evaluate the seven main

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Table 3 Representative test samples.

Sample_A

Sample_B

Sample_C

Sample_D

Sample_E

Sample_F

Sample_G

Sample_H

Sample_I

dimensions and the overall reliability of the 42 evaluation items in this scale. The results indicated that the first five dimensions in the needle-nose plier evaluation item scale achieved reliability standards when compared with the 0.8 reliability coefficient value for the standards of superior scales (Field, 2009). This verified that after item and factor analysis screened inappropriate items, the scale possessed high degrees of stability and reliability. Therefore, this scale can be used as a generalized needle-nose plier design evaluation scale.

Table 4 Partial correlation coefficient of UD evaluation. Needle-nose plier styling design factor

Type

Type scores

Partial correlation coefficient

Springback design

Springs Spring plate None Yes No Single Composite Yes No Simple Average Complex Short Medium Long

0.28547 0.33162 0.39145 0.01709 0.13675 0.09615 0.19231 0.14459 0.04131 0.34829 0.35684 0.00855 0.21766 0.16695 0.07977

0.88107

Serrated plier head Plier handle

Material Textured handle design Styling change

Length

0.23177 0.35043 0.20504 0.60682

0.63573

4.5. UD principles Using needle-nose pliers as an example, this study applied UD to the product design process. Seven design principles and 42 evaluation items were obtained through user evaluations. The evaluation of the seven primary components was not completely independent, and mutual relationships and continuity existed. These seven components were 1) Achieve user's functionality needs, 2) Psychological, spiritual, and social dimensions and User's selfactualization, 3) Aesthetic and Commercial value, 4) Level of work task achievement, 5) Space and environment for Approach and Use, 6) Tolerance, and 7) adjustability. The primary difference between these components and existing UD principles is that the seven evaluation principles proposed in this study demonstrated the order of influence the principles had on the evaluation of the subject. In other words, functionality was the primary consideration factor that influenced needle-nose plier design in the evaluation and the use of needle-nose pliers. Product conformity to user requirements and user-centered thinking are still primary considerations in product design. The second most crucial consideration factor was self-actualization. This indicated that the current DIY trend requires not only the completion of a task during product operation but also the ability of users to achieve a sense of accomplishment. This is self-affirmation on a psychological and spiritual level. The consideration factors, from functionality to adjustability, are listed in descending order based on their importance and level of influence (Table 6). The seven principles proposed by CUD and Satoshi Nakagawa primarily differ from the seven principles proposed in this study in

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Table 5 Factor loadings of the evaluation items (PCA with varimax rotation), only the factor loadings > 0.5 are shown. F1

F2

Achieve user's Psychological, spiritual, and social dimensions functionality and user's self-actualization needs Use of this product does not burden the 0.816 human body. The length and size of this product is 0.804 appropriate. The weight of this product is appropriate. 0.773 The handle design of this product conforms 0.732 to the hand. This product is easy to maintain. 0.731 Operating this product does not cause 0.720 excessive friction on the skin. Everyone can easily use this product. 0.696 Operating this product does not cause 0.689 swelling of the skin. 0.667 Anyone can equably use this product (rightand left-handed people and disabled people). This product is appropriate for people with 0.588 various body types. Operating this product does not cause 0.518 pressure on the hands. Operating this product can produce feedback. Using this product increases life experience. The functionality of this product is excellent. The product is designed for safety and protection. This product is suitable for use by people of all age groups. The design of this product considers diverse groups. The quality of this product is satisfactory. This product can satisfy individual requirements. This product has a humanized design. The exterior of this product has texture. This product is convenient to use. Operating this product can produce a sense of achievement. Long-term use of this product does not cause fatigue. This product has an attractive design and makes people want to possess it. I feel safe using this product. The use of this product does not cause soreness. The styling of this product is aesthetic. This product has broad market value. This product is stable during operation. This product can be used intuitively. This product facilitates the completion of work tasks. This product is practical. The construction of this product is simple. This product conforms to daily habitual use. This product does not stand out in a daily living environment. This product can be easily used in multiple daily living environments. This product can be comfortably operated in a standing or sitting position. This product can be used for various purposes. My caregivers can also use this product. This product does not take up space. This product can be adjusted to match the user's pace and rhythm. Accumulated explanatory rate 19.784 Cronbach's alpha 0.959

F3

F4

F5

F6

Tolerance Aesthetic and Level of work task Space and achievement environment commercial for approach value and use

F7 Adjustability

0.816 0.771 0.738 0.709 0.654 0.609 0.582 0.555 0.531 0.860 0.636 0.617 0.616 0.609 0.597 0.588 0.586 0.553 0.733 0.697 0.625 0.614 0.560 0.557 0.753 0.581 0.563 0.784 0.704 0.538 0.854 35.159 0.954

50.123 0.954

60.666 0.923

68.639 0.873

75.503 0.759

80.524 0.729

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Table 6 Comparison and difference with UD principles. CUD and Mace's 3B principles

Satoshi Nakagawa

The UD principles proposed in this study

Equitable use Flexibility in use

Anyone can use the product equitably. Enable use through various methods

Simple and intuitive use Perceptible information Tolerance for error

Use is simple and easy to understand Can use multiple sensual organs to understand message Improper use of the product will not cause accidents, and the product can be returned to its original shape Reduce physical burden on users Ensure convenient size and space for use Supplement 1 Durability and economics Supplement 2 Quality and aesthetics Supplement 3 Health and environment

Achieve user's functionality needs Psychological, spiritual, and social dimensions and User's self-actualization Aesthetic and Commercial value Level of work task achievement Space and environment for Approach and Use

Low physical effort Size and space for use Optimal design Beauty Good business

that the principles in this study displayed their order of importance in the evaluation. In addition to physiological and task dimension considerations, this study further proposed psychological, spiritual, and social dimensions that reflected the hierarchy of needs proposed by the humanistic psychologist, Abraham H. Maslow. According to this theory, human needs can be divided into hierarchical levels (physiological, safety, love and belonging, esteem, and self-actualization needs) based on their level of importance (Maslow, 1943). People's hierarchy of needs change according to their country's development level (Newstrom and Davis, 1997). Therefore, the physiological and psychological needs of users are both critical concerns in UD development. In addition to basic functionality requirements, the achievement of a user's self-actualization ideals is a factor that cannot be overlooked by designers during product design. The commercial value principle proposed in this study was the third most crucial influence, and one of the important influencing factors. However, existing UD principles generally list commercial value as a supplemental principle and not as a primary influencing principle. A possible reason for this may be related to the aforementioned research concept of this study: the context of UD changes over time. When social change involves commercial orientation, mass production becomes the fundamental objective and requirement for product design. Consequently, if designers do not consider commercial value and economic profit, such as development costs and production procedures during the design stage, reduced product competitiveness and market expansion (compared with that of competing brands and other similar products) can result, and the product will be naturally eliminated from the competitive market. Notably, Mace and Nakagawa both expressed the importance of aesthetics. However, this study integrated aesthetic factors into commercial value principles. The texture, attractiveness, and styling aesthetic evaluation items were all included in the commercial value principle. User requirements toward products are no longer restricted to price or function, and people are beginning to require quality. Users expect to purchase products with a rich design and that has aesthetic properties. In this commercial trend, aesthetics and commercial considerations are becoming inseparable. 5. Design verification 5.1. Universal needle-nose plier design Expert discussions and user opinions were used to obtain and define optimal design factors for needle-nose pliers (springback design, serrated plier head, plier handle material, plier handle

Tolerance Adjustability

textured handle design, degree of plier handle styling change, and overall length). Design verification was conducted to convert user UD evaluation data into an actual design and verify UD factors. According to the users' UD evaluation scale results, quantification theory type I can be used to identify corresponding relationships between evaluation items and needle-nose plier design factors. The results clearly indicated that the existence of a springback design was the primary design factor that influenced needle-nose plier design. The length of the pliers and the degree of plier handle styling change also markedly influenced the design. Therefore, these three design factors should be prioritized in universal needle-nose plier design. Furthermore, the relationship between overall UD achievement and level of preference in the overall evaluation indicated that the springback design, length, and the degree of plier handle styling change were the three main factors that influence universal needle-nose plier design. A possible reason for this may be that despite explaining the UD concepts to the participants prior to the evaluation, the understanding of general users toward UD concepts was not as good as expected. This caused confusion in the participants regarding the evaluation of UD achievement and preference level. However, the design factors preferred by users and obtained through the assessment of evaluation items were a crucial basis for design verification. The discussion of universal needle-nose plier design can be divided into two parts, the plier head and plier handle. In addition to the serrated plier head design, the rigidity of the plier head material was a crucial factor that influenced user selection and the operation of needle-nose pliers. However, typical nonprofessional users cannot accurately detect differences in rigidity. Furthermore, the quality of plier head material is difficult to determine in an experimental process involving only simple tasks and short-term use. The changes or differences of product design happened where directly contact with the product occurred and which primarily for reducing hand strength and motor functioning (McAdams and Kostovich, 2011). Therefore, the plier handles were only redesigned in this study. Sample_E (no springback design, serrated plier head, composite plier handle material, textured plier handle design, complex level of plier handle styling change, and long overall length), which had low evaluation scores, was selected from the representative test samples for improvements. The original plier head was used and the plier handles were redesigned and modified to conform to UD. Design factors for universal needle-nose plier design were obtained through the users' combined evaluation data (with the UD scale) and based on the design factors preferred by users, which were derived from quantification theory type I results. Except for the “fixing” design factor, which involved the original serrated plier

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Table 7 Comparison of styling design factors. Samples

Size

Sample_E

Universal needle-nose plier

head, plier handles and overall length design were considered to produce a universal needle-nose plier (spring plate, springback design, serrated plier head, single plier handle material, untextured plier handle design, average degree of plier handle styling change, and medium length). The selection of plier handle material involved the consideration of a single or composite material design and the use of quantification theory type I to set the hardness of the rubber material based on the user preference evaluation to 70 during model production. A UD scale evaluation was subsequently conducted on Sample_E, which previously had the lowest evaluation scores, and on Sample_G (spring plate, springback design, no serrated plier head, composite plier handle material, untextured plier handle design, average level of plier handle styling change, and medium overall length), which had the highest evaluation scores in Table 7. The purpose was to examine the accuracy and

Sample_G

feasibility of the UD design proposed in this study, and whether the practical applications of the design were improved.

5.2. Design verification evaluation and results In the design verification experiment, sex and age differences were considered and 10 participants (three men and seven women with an average age of 40.80 years and an SD of 14.91) were invited to operate the universal needle-nose plier, Sample_E, and Sample_G to perform simple work tasks. The generalized needle-nose plier design evaluation scale (after item and factor analysis was used to eliminate inappropriate items, 42 evaluation items and two combined evaluation items remained, totaling 44 evaluation items) was used in the reevaluation.

Fig. 3. UD achievement of design verification.

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Fig. 4. Design process of UD product.

For the seven main design principles, the user evaluation scores for each evaluation item were averaged to obtain user evaluations scores for each principle, which are displayed in the radar chart (Fig. 3). The results indicated differences in the evaluations. The verification results indicated that the needle-nose pliers designed in this study produced considerable improvements in the evaluation of each principle, the distribution of each principle was equal, and the pliers received high scores. This study explored whether the existence of a springback design was the primary factor that influenced design. The results of the aforementioned experiment indicated that needle-nose pliers with a springback design (regardless of whether it contains springs or a spring plate) produced considerably higher overall evaluation scores than that of needle-nose pliers without a springback design. Other main factors include the overall length and the degree of plier handle styling change. Regarding sex differences, the width (not including thumbs) and length of men and women's hands differ considerably. Statistical data revealed that the average hand width of men and women between the ages of 18 and 64 years differs by approximately 7e10 mm, and the average hand length differs by approximately 10e15 mm (Wang et al., 2002). This indicates that these two physical differences were factors that influenced the grip evaluation of needle-nose pliers.

6. Conclusion and recommendations Investigations have indicated that UD scales are generally used for postevent evaluations. During product design, market surveys are conducted and the results are used to determine design orientation. However, product design is often based on the subjective thoughts of designers, and does not involve accurately converting the opinions of the majority of users into design factors that can serve as a design reference. This suggests that the UD concept of suitability for most people cannot be implemented in the design process. The UD scale was used in the user evaluation to determine the UD achievement level of the product proposed in this study, and product design revisions were made based on the results of the participant evaluations. Market surveys, a literature review of studies involving UD and hand-tool comfort, data extracted from needle-nose plier user experience questionnaires, and existing UD principles were used in this study to develop a new UD scale. Quantitative analysis was used to optimize the newly developed generalized needle-nose plier evaluation scale and eliminate inappropriate evaluation items. It can be found that the concept of UD is developing over time and be varied in category of products and services. Quantification theory type I was used to convert user evaluation results into

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product design factors, which provided designers with references during product design and development. Though the case study of universal plier design was analytic, the proposed methodology was demonstrated that could be applied to determine the appropriate UD scale and design factors were transferred successfully from user evaluation for UD applications. UD concepts were introduced into initial product design, which included user opinions and participation. The proposed universal product design and design process is shown in Fig. 4. The proposed methodology presents here can be applied by designers in developing future product designs and evaluation models. As guidance or rules of universal design are discovered and refined, it can be presented as a simple checklist, design rule of thumb, or a computer-aided lookup table to designers (Sangelkar et al., 2012). Future efforts will focus on improving the efficiency of this universal product design process and developing design strategies for product development platform that share common factors and product family with some certain unique factors. Furthermore, the cross fields of product types are valuable to be considered since there are several UD studies and design guidance focus on architectural systems. There are challenges remains on Universal Design practice. The evaluation of UD is not only on physical or functional level but on metal level and cognition. References Aptel, M., Claudon, L., Marsot, J., 2002. Integration of ergonomics into hand tool design: principle and presentation of an example. Int. J. Occup. Saf. Ergon. 8 (1), 107e115. Bryman, A., Cramer, D., 1997. Quantitative Data Analysis with SPSS for Windows. Routledge, London. Charness, N., 1981. Aging and skilled problem solving. J. Exp. Psychol. General 101 (1), 21e38. Christensen, A.D., Bishu, R., 2000. Hand tool design: are biomechanical criteria the same as aesthetic criteria? A preliminary study. In: Proceedings of the IEA 2000/HFES 2000 Congress, vol. 4, pp. 564e577. Clarkson, J., Coleman, R., Keates, S., Lebbon, C., 2003. Inclusive Design: Design for the Whole Population. Springer, London. Clarkson, J., Cardoso, C., Hosking, I., 2007. Product evaluation: practical approaches. In: Coleman, R., Clarkson, J., Dong, H., Cassim, J. (Eds.), Design for Inclusivity. Gower, Aldershot, UK, pp. 181e196. Clarkson, J., 2008. Human capability and product design. In: Schifferstein, H.N.J., Hekkert, P. (Eds.), Product Experience. Elsevier, San Diego, CA, pp. 165e198. Clarkson, J., Langdon, P., Goodman-Deane, J., Robinson, P., 2008. In: Proceedings of 4th Cambridge Workshop on Universal Access and Assistive Technology. Fitzwilliam College, Cambridge. Connell, B., Jones, M., Mace, R., Mueller, J., Mullick, A., Ostroff, E., 1997. The principles of universal design. Retrieved 14.07.09, from: http://www.design.ncsu.edu/cud/ about_ud/udprincipleshtmlformat.html. Dempsey, P.G., McGorry, R.W., Leamon, T.B., O'Brien, N.V., 2002. Bending the tool and the effect on human performance: further investigation of a simulated wire-twisting task. AIHA J. 63, 586e593. Fellows, G.L., Freivalds, A., 1991. Ergonomics evaluation of a foam rubber grip for tool handles. Appl. Ergon. 22 (4), 225e230. Field, A., 2009. Discovering Statistics Using SPSS. Sage, London. Field, A., 2000. Discovering Statistics Using SPSS for Windows. Sage, LondoneThousand OakseNew Delhi. Goodman-Deane, J., Ward, J., Hosking, I., Clarkson, J., 2014. A comparison of methods currently used in inclusive design. Appl. Ergon. 45 (4), 886e894. €-Rahansto, J., Mattila, M., 1999/2000. Ergonomic design of Haapalainen, M., Kivisto non-powered hand tools: an application of quality function deployment (QFD). Occup. Ergon. 2 (3), 179e189. Hirtz, J., Stone, R., McAdams, D., Szykman, S., Wood, K., 2002. A functional basis for engineering design: reconciling and evolving previous efforts. Res. Eng. Des. 13 (2), 65e82. Japan Ergonomics Society, 2007. The Universal Design Practical Guidelines. Kyoritsu Shuppan Co., Ltd. Kanamori, H., Misugi, K., 2004. Challenges for Universal Design in Vehicle Development. International Association for Universal Design. From: http://www.iaud. net/dayori-f/data/rio_report/toyota1_ppt.pdf.

Kawauchi, Y., 2001. Universal Design: a Reconsideration of Barrier-Free. Institute for Human Centered Design, Kyoto, ISBN 978-476-1522-58-2. Keates, S., Clarkson, J., 2003. Countering Design Exclusion: an Introduction to Inclusive Design. Springer, London. Kostovich, V., McAdams, D.A., Moon, S.K., 2009. Representing user activity and product function for universal design. In: Proceeding of the 2009 ASME Design Engineering Technical Conferences & Computers and Information in Engineering, San Diego, CA, USA. Kuijt-Evers, L.F.M., Groenesteijn, L., Looze, M. P. de, Vink, P., 2004. Identifying factors of comfort in using hand tools. Appl. Ergon. 35 (5), 453e458. Kuijt-Evers, L.F.M., Bosch, T., Huysmans, M.A., Looze de, M.P., Vink, P., 2006. Association between objective and subjective measurements of comfort and discomfort in hand tools. Appl. Ergon. 38 (5), 643e654. Langdon, P., Clarkson, J., Robinson, P., 2008a. Designing Inclusive Futures. Springer, London. Langdon, P., Persad, U., Clarkson, J., 2008b. Operationalizing analytical inclusive design evaluation. In: International Conference on Contemporary Ergonomics, Nottingham, UK. Mace, R., 1970. 3-B Principles of Universal Design. Accessible Housing Center. Marsot, F., Claudon, L., 2004. Design and ergonomics. Methods for integrating ergonomics at hand tool design stage. Int. J. Occup. Saf. Ergon. 10, 13e23. Maslow, A.H., 1943. A theory of human motivation. Psychol. Rev. 50 (4), 370e396. McAdams, D.A., Kostovich, V., 2011. A framework and representation for universal product design. Int. J. Des. 5 (1), 29e42. Mitsufuji, Y., Uchida, T., 1993. Using and promoting house of qualities. In: Akao, Y. (Ed.), QFD: Quality Function Deployment: Integrating Customer Requirements into Product Design. Productivity Press, Cambridge, pp. 53e81. Moon, S.K., McAdams, D.A., 2009. Universal design platform and family design for uncertain market. In: Proceeding of International Conference on Engineering Design ICED' 09, Stanford, CA, USA. Moon, S.K., McAdams, D.A., 2010. A platform-based strategic design approach for universal products. Int. J. Mass Cust. Eng. Conf. 3 (3), 227e246. Morimoto, K., Kurokawa, T., Takemoto, K., Hori, T., Kushiro, N., Inoue, M., 2001. Protocol analysis on usability of remote controllers of household appliances for elderly people. In: 5th Asian Design Conference, Korea, C13. Nippashi, N., Aoki, M., Otake, S., Kishi, C., Terauchi, F., 2006. New Concept and Its Methods of Designing with Ordinary Citizens e Design for Ourselves. Department of Design and Architecture, Faculty of Engineering, Chiba University, Chiba-shi, Japan. Newstrom, D., Davis, K., 1997. Organizational Behavior. Human Behavior at Work. University of Minnesota, Duluth, ISBN 0-07-114538-9. Nakagawa, S., 2006. Textbook for Universal Design. Long Sea Int'l Book Co., Taipei City, ISBN 978-986-7022-05-9. Otto, K.N., Wood, K.L., 2001. Product Design: Techniques in Reverse Engineering and New Product Development. Prentice Hall, NJ, USA, Upper Saddle River. Salthouse, T.A., 1992. Reasoning and Spatial Abilities. In: Hand Book of Aging and Cognition. Erlbaum, NJ, USA, pp. 167e211. Sangelkar, S., McAdams, D.A., 2010. Adapting ADA architectural design knowledge to product design: groundwork for a function based approach. In: Proceeding of the ASME 2010 International Conferences & Computers and Information in Engineering Conference, Montreal, QC, CA. Sangelkar, S., McAdams, D.A., 2012. Adapting ADA architectural design knowledge for universal product design using association rule mining: a function based approach. J. Mech. Des. 134, 071003-1e071003-15. Sangelkar, S., Cowen, N., McAdams, D.A., 2012. User activityeproduct function association based design rules for universal design. Des. Stud. 33, 85e110. Sawada, K., Fukano, S., Sakayori, E., Kosaka, M., 2006. Creation of a tool for universal design development evaluation UD-checker creation and examples of use. In: Proceeding of the 2nd International Conference for Universal Design in Kyoto 2006. Vanderheiden, G., Tobias, J., 2000. Universal design of consumer products: current industry practice and perceptions. In: Proceedings of the IEA. Vink, P., Overbeeke, C.J., Desmet, P.M.A., 2005. In: Vink, P. (Ed.), Comfort and Design: Principles and Good Practice. CRC Press, Boca Raton, FL, pp. 1e12. Waller, S.D., Langdon, P., Cardoso, C., Clarkson, J., 2008. Calibrating capability loss simulators to population data. In: International Conference on Contemporary Ergonomics, Nottingham, UK. Waller, S.D., Goodman-Deane, J., Langdon, P., Johnson, D., Clarkson, J., 2009. Developing a method for assessing product inclusivity. In: International Conference on Engineering Design ICED' 09, Stanford, CA, USA. Waller, S.D., Langdon, P., Clarkson, J., 2010. Using disability data to estimate design exclusion. Univers. Access Inf. Soc. 9 (3), 195e207. Wang, M.-J., Wang, M.-Y., Lin, Y.-C., 2002. Anthropometric Data Book of the Chinese People in Taiwan. The Ergonomics Society of Taiwan, Hsinchu City, ISBN 95730149-0-4. Zhang, L., Helander, M.G., Drury, C.G., 1996. Identifying factors of comfort and discomfort in sitting. Hum. Factors 38 (3), 377e389.