Increasing testing severity in multi-group designs

Introduction A little over a year ago Patrick Forscher wrote a very nice blog post about a simple way to increase the severity of a hypothesis test in a multi-group experimental design (in this case one factor, 3-group design). He highlights the main problem as the following: Multi-group designs are the workhorse of scientific psychology. Multi-group designs apply to any grouping of people, within-person states, situations, or stimuli; interest typically centers around the either the means or conditional means within each group.