14.6 Thompson, Schellenberg, and Husain (2001) tested the “Mozart effect,” the effect on tests of spatial abilities after listening to music by Mozart. Twenty-four participants listened to a tape of music by either Mozart or Albinoni (Group, g=2). They were tested on measures of spatial relations, arousal, mood, and enjoyment after listening to the music and also after a period of silence (Condition, c=2). The order of the two conditions was counterbalanced with half of the subjects receiving the music first and half receiving the silence first (Order, o=2).

(a) The F for Groups on the arousal scores was 6.20. What are the values of and for this effect? According to Cohen’s (1988) guidelines, is the effect small, medium, or large?

(b) Assuming the effect estimated in part (b), what power did the experiment have? Is nonsphericity a potential problem in this calculation? Would it be if we were calculating power for the effect of conditions? Explain,

(c) If we were to redo the experiment, assuming a medium effect on arousal by Cohen’s standards, how many subjects would we need to attain power of .8?