A group of students in your intro stats class design an expe

A group 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?

Solution

Since they brought two different brands, they introduced two potential sources of variation 1) type of pop corn(freezer kept or rom temparature) 2) Brands. But instead of acknowledging the variation due to brands they alloted mix of bags to each group thus violating \"Blocking\" assumption of the Design.