Agroup of students in your intro stats class design an experiment to test whether popcorn stored in the freezer pops better (fewer kernels left un-popped) than room temperature popcorn. two group members do the shopping separately and realize too late that they've bought two different brands. if they ignore this and randomly assign a mix of bags to each treatment group, what principle of experiment design have they ignored?

a group of students in your intro stats class desi