Weighted objectives method
What Is the Weighted Objectives Method?
The Weighted Objectives Method is an evaluation method for comparing design concepts based on an overall value per design concept. The biggest disadvantage of using the Datum method or the Harris profile is that the scores per criterion cannot be aggregated into an overall score of the design alternative. This makes a direct comparison of the design alternatives difficult. The Weighted Objectives Method does exactly this: it allows the scores of all criteria to be summed up into an overall value per design alternative.
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 can be of less importance than appealing aesthetics. The Weighted Objectives Method involves assigning weights to the different criteria. This allows the decision-maker to take into account the difference in importance between criteria.
When Can You Use the Weighted Objectives Method?
The Weighted Objectives Method is best used when a decision has to be made between a select 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.
How to Use the Weighted Objectives Method?
A limited number of concepts.
A chosen concept.
- Select the criteria according to which the selection will be made. These criteria should be derived from the programme of requirements (note that probably not all requirements are applicable at this stage of the design process).
- Choose 3 to 5 concepts for selection.
- Assign weights to the criteria. The criteria should be appointed weights according to their importance for the evaluation. To determine the weight factor of the criteria it is recommended that you compare the criteria in pairs to attribute a weight factor. Rank each of the weights on a scale from 1 to 5 (you can also decide on a total sum of the weights of the criteria, for example 100). Make sure you discuss the trade-offs between the criteria. Trade-offs will have to be made when weights are assigned to the individual criteria (when you are determining which of the weights are more important).
- Construct a matrix, with the criteria in rows, and the concepts in columns.
- Attribute values to how each concept meets a criterion. Rank the scores of the concepts from 1 to 10.
- Calculate the overall score of each concept by summing up the scores on each criterion (make sure you take into account the weight factor).
- The concept with the highest score is the preferred concept.
Tips and Concerns
- This method should be carried out intelligibly, while discussing and reviewing both the weights assigned to the criteria and the scores of the concepts according to all the criteria.
References and Further Reading
- Roozenburg, N.F.M. and Eekels, J. (1995) Product Design: Fundamentals and Methods, Utrecht: Lemma.
- Roozenburg, N. and Eekels, J. (1998, 2nd ed.) Product Ontwerpen: Structuur en Methoden, Utrecht: Lemma.