Need to show through simulation that aggregating data by items is going to cause a lot of potentially important variation from being hidden, leading to possible Type I error inflation (of course, it depends on the particular situation being simulated---maybe show a case where this doesn't happen).
Need to show through simulation that aggregating data by items is going to cause a lot of potentially important variation from being hidden, leading to possible Type I error inflation (of course, it depends on the particular situation being simulated---maybe show a case where this doesn't happen).