Step 3: Rank the Concepts
After rating all the concepts, the team sums the number of "better than," "same as," and "worse than" scores and enters the sum for each category in the lower rows of the matrix. From our example in Exhibit 8-5, concept A was rated to have two criteria better than, five the same as, and none worse than the reference concept. Next, a net score can be
calculated by subtracting the number of "worse than" ratings from the "better than" ratings.
Once the summation is completed, the team rank-orders the concepts. Obviously, in general those concepts with more pluses and fewer minuses are ranked higher. Often at this point the team can identify one or two criteria that really seem to differentiate the concepts.
Step 4: Combine and Improve the Concepts
Having rated and ranked the concepts, the team should verify that the results make sense and then consider if there are ways to combine and improve certain concepts. Two issues to consider are:
• Is there a generally good concept that is degraded by one bad feature? Can a minor modification improve the
overall concept and yet preserve a distinction from the other concepts?
• Are there two concepts that can be combined to preserve the "better than" qualities while annulling the "worse than" qualities?
Combined and improved concepts are then added to the matrix, rated by the team , and ranked along with the original concepts. In our example, the team noticed that con cepts D and F could be combined to remove several of the "worse than" ratings to yield a new concept, DF, to be considered in the next round. Concept G was also considered for revision. The team decided that this concept was too bulky, so the excess storage space was removed while retaining the injection technique. These revised concepts are shown in Exhibit 8-6.
Step 5: Select One or More Concepts
Once the team members are satisfied with their understanding of each concept and its relative quality, they decide which concepts are to be selected for further refinement and analysis. Based upon previous steps, the team will likely develop a clear sense of which are the most promising concepts. The number of concepts selected for further review will be limited by team resources (personnel, money, and time). In our example, the team selected concepts A and E to be considered along with the revised concept G+ and the new