12. A psychologist interested in animal learning conducts an experiment to determine the effect of adrenocorticotropic hormone (ACTH) on avoidance learning. Twenty 100-day-old male rats are randomly selected from the university vivarium for the experiment.

Of the 20, 10 randomly chosen rats receive injections of ACTH 30 minutes before being placed in the avoidance situation. The other 10 receive placebo injections. The number of trials for each animal to learn the task is given here:

a. What is the nondirectional alternative hypothesis?

b. What is the null hypothesis?

c. Using 0.012 tail, what do you conclude?

d. What error may you have made by concluding as you did in part c?

e. To what population do these results apply?

f. What is the size of the effect? biological

ACTH Placebo 58 74 73 92 80 87 78 84 75 72 74 82 79 76 72 90 66 95 77 85