Overall, rats that received a drug took longer to find their way out of a maze than rats that received a placebo, F (1, 57) = 7.23, p

Question

Overall, rats that received a drug took longer to find their way out of a maze than rats that received a placebo, F (1, 57) = 7.23, p < 0.05; the drug had a large effect on albino rats and virtually no effect on wild-bred rats, F (1, 57) = 11.01, p < 0.05.However, there was no overall difference in the time of albino rats compared to that of wild-bred rats, F (1, 57) = 1.11, p > 0.10.Which effect(s) must be present for these results to be true?
A) main effect of drug
B) main effect of rat species
C) interaction of drug and rat species
D) main effect of drug and an interaction of drug and rat species

Quizplus · Accepted Answer

The results show a significant main effect of drug (rats that received a drug took longer to find their way out of a maze than rats that received a placebo) and an interaction effect between drug and rat species (the drug had a large effect on albino rats and virtually no effect on wild-bred rats). There was no significant main effect of rat species (no overall difference in the time of albino rats compared to that of wild-bred rats), but this is not necessary for the overall results to be true. Therefore, the best choice is D, which includes both a main effect of drug and an interaction of drug and rat species.

Overall, Rats That Received a Drug Took Longer to Find