Chapter 9, Problem 14P

]14. Many animals, including humans, tend to avoid direct eye contact and even patterns that look like eyes. Some insects, including moths, have evolved eye-spot patterns on their wings to help ward off predators. Scaife (1976) reports a study examining how eye-spot patterns affect the behaviour of birds. In the study, the birds were tested in a box with two chambers and were free to move from one chamber to another. In one chamber, two large eye-spots were painted on one wall. The other chamber had plain walls. The researcher recorded the amount of time each bird spent in the plain chamber during a 60-minute session. Suppose the study produced a mean of $M=34.5$ minutes on the plain chamber with $SS=210$ for a sample

of $n=15$ birds. (Now: If the eye spots have no effect. then the birds should spend an average of $\mu =30$ minutes in each chamber.)

a. Is this sample sufficient to conclude that the eyes pots have a significant influence on the bird’s behaviour? Ike a two-tailed test with $\alpha =.05$.

b. Compute the estimated Cohen’s d to measure the size of the treatment effect.

c. Construct the 90% confidence interval to estimate the mean amount of time spent on the plain side for the population of birds.