What is the main reason we might prefer to use a Latin Square design over a complete counterbalancing design?

A. Because they include all possible sequences

B. To reduce order effects

C. Because there are too many participants

D. Because there are too many conditions

A 2 x 2 factorial experiment produces a set of means in a graph that looks like an upright 'X' shape. This likely means there is:

A. Both main effects and an interaction

B. A main effect of factor 2

C. A main effect of factor 1

D. An interaction