Delft Design Guide: Evaluate & Decide

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Delft Design Guide: Evaluate & Decide

  1. 1. EVALUATE & DECIDEThis section contains methods that can help you to evaluate design proposals and make decisions while designing. INTERACTION PROTOTYPING & EVALUATION PRODUCT USABILITY EVALUATION PRODUCT CONCEPT EVALUATION EMOTION MEASUREMENT INSTRUMENT (PREMO) HARRIS PROFILE EVR DECISION MATRIX C-BOX ITEMISED RESPONSE & PMI DATUM METHOD VALUE WEIGHTED OBJECTIVES COST PRICE ESTIMATION 131 133 135 137 139 141 143 145 147 149 151 153
  2. 2. REFERENCES & FURTHER READING: Harris, J.S., 1961. New Product Profile Chart. Chemical and Engineering News, 17 April, 39(16), pp.110-118. / Roozenburg, N.F.M. and Eekels, J.*, 1995. Product Design: Fundamentals and Methods. Utrecht: Lemma. When can the method be used? A Harris Profile is based on the design requirements for your design. Whenever a number of alternative product concepts need to be compared and evaluated, the Harris Profile can be used to make your – or your team’s – evaluation explicit. As designers make some of their evaluations intuitively, the Harris Profile can help you to make those intuitions explicit so that you can discuss them with other stakeholders. A Harris Profile can be useful during each phase of the design process, but typically it is used after an idea generation phase when ideas or concepts need to be eliminated. How to use the method? Create a Harris Profile for each alternative design concept. A Harris Profile consists of an assessment of how the concept meets each of the listed design requirements. The evaluations are relative, comparing the different concepts in terms of their performance in each criterion. A four- point scale is typically used to score the concepts. You should interpret the meaning of the scale positions: -2 = bad, -1 = moderate, et cetera. Thanks to the visual representation, decision makers can quickly view the overall score of each design alternative for all the criteria, and compare them easily. An important role of the Harris Profile is to make your evaluation explicit and easy to understand: it can help to stimulate discussion with your project’s stakeholders in the early phases of design, when design requirements typically change as the concepts evolve and you gain a greater shared understanding of the design problem. Possible procedure STEP 1 List the design requirements as fully as possible and rank them according to their importance for the design project. STEP 2 Create a four-point scale matrix next to each requirement, coded -2, -1, +1, and +2. STEP 3 Create a Harris Profile for each of the design alternatives by evaluating the relative performance of each alternative with respect to the requirements. STEP 4 Draw the profile by marking the scores in the four-point scale matrix for all the criteria. STEP 5 Present the profiles next to each other to allow discussion with stakeholders and to determine which design concept has the best overall score. Limitations of the method • The four-point scales should be interpreted differently for each requirement and are not necessarily comparable. • It is tempting to interpret Harris Profiles as ‘true’ representations of the performance of design alternatives. However, it is important to realise that the performance assessment of design concepts is typically an intuitive prediction of performance, with low reliability. • The primary function of the profile is to communicate the evaluations that you have made after careful discussions and deliberations, and if necessary to open up discussion to sharpen the definitions of requirements or improve design concepts. Tips & Concerns • Use drawings to represent concepts in each profile – this will enhance the communicability of your profiles. • If possible, cluster the criteria. • Design is not a linear process, so you might discover new design requirements while evaluating concepts. You can add those requirements to your Harris Profile and enhance the accuracy of your evaluation. • When attributing the -2 or +2 values to a criterion, be sure to colour all the blocks in the Harris Profile. Only then can you create a quick visual overview of the overall score of a design alternative. HARRIS PROFILE A Harris Profile is a graphic representation of the strengths and weaknesses of design concepts with respect to predefined design requirements. It is used to evaluate design concepts and facilitate decisions on which concepts to continue with in a design process. In a Harris profile, the main design requirements are ranked in order of importance with the most important one on top. An even number of possible scores are used to prevent neutral scoring. This way of evaluating is helpful when ideas and designs are still conceptual and not worked out in detail: imagine the black squares are building blocks of a tower. By viewing ‘which way the tower of blocks would fall’, a choice can be made. Colours should not be used and scores can not be added up. In general, all decision making methods are meant to initiate discussion within the development team and to structure the process of chosing. In the lower example, another design prevails because the design requirements are listed in another order. It shows how another team could have a different view on what is important. Speed D E L F T D E S I G N G U I D E — 1 3 9 EVALUATE & DECIDE
  3. 3. WEIGHTED OBJECTIVES REFERENCES & FURTHER READING: Roozenburg, N.F.M. and Eekels, J.*, 1995. Product Design: Fundamentals and Methods. Utrecht: Lemma. / Roozenburg, N.F.M. and Eekels, J.*, 1998. Product Ontwerpen: Structuur en Methoden. 2nd ed. Utrecht: Lemma. When can the method be used? The Weighted Objectives Method is best used when a decision has to be made between a selected number of design alternatives, design concepts or principal solutions. Usually, the Weighted Objectives Method is used when evaluating design concepts, and to make a decision as to which design concept should be developed into a detailed design. The Weighted Objectives Method enables you to sum up the scores of all criteria into a numerical value for each design alternative. How to use the method? The Weighted Objective Method assigns scores to the degree to which a design alternative satisfies a criterion. However, the criteria that are used to evaluate the design alternatives might differ in their importance. For example, the cost price might be of less importance than appealing aesthetics. The Weighted Objectives Method allows you to take into account the difference in importance between criteria by assigning weights according to their importance for the evaluation. You can rank each of the weights on a scale from 1 to 5 or decide on a total sum of the weights of the criteria, for example 100. Possible procedure STEP 1 Select the criteria according to which the selection will be made. STEP 2 Choose three to five concepts for evaluation. STEP 3 Assign weights to the criteria. Step 4 Construct a matrix, with the criteria in rows and the concepts in columns. STEP 5 Attribute values to how each concept meets a criterion. Rank the scores of the concepts from 1 to 10. STEP 6 Calculate the overall score of each concept by summing up the scores on each criterion (make sure you take into account the weight factor). STEP 7 The concept with the highest score is the preferred concept. Tips & Concerns • This method should be carried out coherently, while discussing and reviewing both the weights assigned to the criteria and the scores of the concepts according to all the criteria. • To determine the weight factors of the criteria it is recommended that you compare the criteria in pairs to attribute a weight factor to each of them. The Weighted Objectives Method is an evaluation method for comparing design concepts based on the overall value of each design concept. From left to right: paperclip lamp, paperclip alphabet, staple city. D E L F T D E S I G N G U I D E — 1 5 1 EVALUATE & DECIDE By attributing weight factors to design requirements, the choice of a certain design can be precisely motivated. Design proposals should be worked out in detail so that they can be scored. Like all methods for evaluation, the main aim is to initiate a structured discussion and to communicate the processes of choice within a development team. The highest-scoring proposal is not necessarily the winner. By analysing the scores, strong features of different proposals can be combined into a new one.

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