Evaluation tests will always focus on the total sale and consume situation. The test/interview starts with a general description of the situation. Slowly the test person is introduced to more and more elements in the whole sale and consumes situation. And in the end the interview will focus on specific problems.
Both focus groups and programmed interviews must be planed. This plan must be designed in a tree structure so the test persons are able to control some of the direction in the process. And in the same time you shall be in control of the process in order to include important specific subjects in the interview. The test person shall sense that he/she is in control over the direction. But you shall be in control of the whole situation being preparing new questions what ever happens.
All who have used these methods are always amazed over all the unexpected details coming up in the interviews. And you have really more information after and know the real way your packaging is used. The new data will have a qualitative nature as: I use the packaging like this….. But you do not know the percentage with that behaviour.