Figure: a Researcher Was Interested in the Effects of Arousal and and Personality

Multiple Choice

Figure:
A researcher was interested in the effects of arousal and personality on individuals' GRE test performance.The personality variable he examined was individuals' level of introversion-extraversion.Based on questionnaire responses,each participant was classified as an "extravert" or an "introvert." The researcher manipulated arousal level by giving caffeine to participants prior to administering a practice GRE test.Participants were randomly assigned to a high-caffeine condition,a medium-caffeine condition,or the no-caffeine conditions.All participants then completed a practice version of the quantitative portion of the GRE.
Suppose the researcher observed the following means for each group:
-The means for the main effect of personality are

A) 500 and 700.
B) 600,600,and 600.
C) 600 and 600.
D) The means cannot be determined in this design.