Our client wished to test 4 different product variants with a key, but difficult (& expensive) to find segment of consumers. Therefore, we needed each consumer to test all 4x products for an extended period in their home environment. But we needed to be careful the respondent understood the task in hand and did not mix up the testing rotation.
Respondents were therefore recruited, personally briefed and handed the first two products. After trial and completion of the first questionnaire, only then did we hand over the second two products.
In this way the quality and integrity of the research was enhanced. As a consequence, the results produced a significant preference for one of the product variants and also provided guidance for a couple of minor product enhancements that contributed to a successful launch.