I'm working on a problem where I have a sample of 200 people. I have a total of 5 concepts which are viewed by each respondent, but are rotated so there is "no" bias due to viewing order. Obviously each concept does not have the opportunity to be in each of the 5 possible viewing positions equally, but each concept is placed in the first position an equal number of times (i.e. each concept is seen in the first position by 40 people). Now, I want to compare rating scores from concept to concept. I'm not sure that a standard t-test would do the trick here. People I know in the market research industry have said that when a single respondent views multiple concepts, weaker concepts viewed in the last position (5th in this case) wind up with lower scores than if they were in the first position. Further, stronger concepts wind up with higher scores if viewed in the last position than if they were viewed in the first position. I would think this affects variance in some way even though the concepts are viewed in a randomized order from respondent to respondent. So finally my question: Which test for significance would I use to test each concept against each other (or just one of them compared to another one)? These are all proportions such as 30% rated Definitely Would Buy (top box of a 5-point scale). Thanks in advance!