Question

A government-sponsored telephone counseling service for adolescents tested whether the length of calls would be affected by a special telephone system that had a better sound quality. Over the past several years, the lengths of phone calls (in minutes) were normally distributed with Population Mean = 18 and Population Standard Deviation = 8. They arranged to have the special phone system loaned to them for a day. On that day, the mean length of the 46 calls they received was 21 minutes. Test whether the length of calls has changed using the .05 significance level.

1. Carry out a Z test using the 5 steps of hypothesis testing (5 points)

2. Make a drawing of the distributions involved (2 points)

3. Explain your answer to someone who doesn't know anything about statistics (2 points)

4. Figure the 95% Confidence interval (2 points)

Answer 1