A biopsychologist is studying the role of the role of marijuana (THC) on aggression in rats. Specifically, the researcher asserts that the influence of large doses of marijuana will make rats more aggressive. Twenty two rats are randomly assigned to one of two groups. The active ingredient in marijuana is called delta-9 THC. One group of 11 rats serves as a control group and receives a placebo (via injection). A second group of 11 different rats receives a large dose of delta-9 THC via injection. These rats have not been paired up on any trait. Then the researcher tests the animals by recording the number of aggressive responses each of the rats display in a 30 minute test period one hour after the rats were injected. The data are presented below, and represent the number of aggressive responses per rat in each group.

X1

Large dose of delta-9 THC Group X2 Placebo Group

17 9 15 12 18 11 14 12 20 15 11 12 15 10 20 19 18 14 19 9 12 10

Which of the following are the correct statements of the null and alternate hypotheses, H0 and HA ?

H0: µ1 = µ2 and HA: µ1 µ2

H0: µ1 µ2 and HA: µ1 = µ2

H0: µ1 > µ2 and HA: µ1 µ2

H0: µ1 µ2 and HA: µ1 > µ2

H0: µ1 < µ2 and HA: µ1 µ2

H0: µ1 µ2 and HA: µ1 < µ2