Let’s suppose that you want to determine the efficacy index (on the 10 to 100 scale) that corresponds to the coordinate 5 (on the 1 to 7 scale).
A graph such as the one depicted in Figure 60 will facilitate the interpolation process. This graph is available in the additional graphs, accessible through a link at the top of the study. It is obtained by plotting the actual characteristics of all marketed brands on the horizontal axis and the corresponding perceptions on the vertical axis. Each marketed brand corresponds to a data point on the graph. There is one such graph for each dimension: efficacy, safety, etc. The segment ideal values are indicated on the vertical axis.
Doing the interpolation is straightforward with this chart. Simply plot the desired coordinate on the vertical axis, 5 in our example. Follow a horizontal line until you intersect the green curve, and then follow a vertical line starting at the point of intersection. You can now read the physical characteristic (index) corresponding to the desired position 5. This is 69 in our example.
The curve on our example is almost a straight line. This is not always the case, especially when several brands have been positioned or repositioned on the market through the use of perceptual objectives.
Repeat the process above for each dimension for which you need to find the physical characteristic corresponding to a desired coordinate.
Figure 60 – Relationship between attributes and perceptions – Semantic scales