A biopsychologist is studying the role of the role of marijuana (THC) on aggress
ID: 3049480 • Letter: A
Question
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.
X2 Placebo Group
Complete step 3 of the hypothesis testing procedure and calculate t using which ever formula you prefer. Round to the nearest hundredths place. If your calculated t is not identical to one of the values below, but within plus or minus 0.16 of an answer below, assume it's a rounding error and select the answer that is closest to your calculated value. Ignore the minus sign if your calculated t is negative.
X1Large 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 10Explanation / Answer
f) is correct
t-Test: Two-Sample Assuming Equal Variances Variable 1 Variable 2 Mean 16.27272727 12.09090909 Variance 9.618181818 8.890909091 Observations 11 11 Pooled Variance 9.254545455 Hypothesized Mean Difference 0 df 20 t Stat 3.223806339 P(T<=t) one-tail 0.002129138 t Critical one-tail 1.724718243 P(T<=t) two-tail 0.004258276 t Critical two-tail 2.085963447