134 Training zoo animals. Teaching of Psychology (May 1998)

did a study in which students assisted in the training of zoo animals. A sample of 15 psychology students rated “The Training Game” as a “great” method of understanding the animal’s perspective during training on a 7–1 point scale

(where 1 = strongly disagree and 7 = strongly agree ).

The mean response was 5.87, with a standard deviation of 1.51.

a. Construct a 95% confidence interval for the true mean response of the students.

b. Suppose you want to reduce the width of the 95% confidence interval to half the size obtained in part a . How many students are required in the sample in order to obtain the desired confidence interval width?