Why is it important to be single-minded in concept test body copy?

What will be an ideal response?

The rule of "one idea-one concept" is important because it reduces ambiguity in data interpretation. Successful concept test research allows one to determine the relationship between the core idea expressed in the concept and consumer response. When the concept body copy single-mindedly focuses on one core idea, positive or negative consumer response can reasonably be attributed to the relative appeal of the concept's core idea and expressed product benefit. On the other hand, placing multiple ideas or benefits in the concept's body copy confuses the interpretation of the results. An overall neutral response to the concept might reflect an overall blase consumer response, or it might reflect the average of two extremes - strong positive response to one core idea and a strong negative response to a second core idea in the same concept.