14. A physiologist conducts an experiment designed to determine the effect of exogenous thyroxin (a hormone produced by the thyroid gland) on activity. Forty male rats are randomly assigned to four groups such that there are 10 rats per group. Each of the groups is in jected with a different amount of thyroxin. Group 1 gets no thyroxin and receives saline solution instead. Group 2 receives a small amount, group 3 a moderate amount, and group 4 a high amount of thyroxin. After the injections, each animal is tested in an open-fi eld apparatus

a. What is the overall null hypothesis?

b. Using  0.05, what do you conclude?

c. What is the size of the effect, using vˆ2?

d. Evaluate the a priori hypothesis that a high amount of exogenous thyroxin produces an effect on activity different from that of saline. Use  
0.052 tail.

e. Use the Tukey HSD test with   0.05 to compare all possible pairs of means. What do you conclude?
biological