Question

A random sample of 35 Hollywood movies made since the year 2010 had a mean length of 121.6 minutes, with a sample standard deviation of 20.4 minutes.

(a) (10 points) Construct a 95% confidence interval for the true mean length of all Hollywood movies made since 2010. Here are some questions to consider. You must show all your work to receive full credit.

i. Which standard deviation are you given?, What is the error formula?, How do we compute the critical value?

(b) (2 points) Explain the confidence interval, what can you say about the population mean μ?

(c) (3 points) There were three Ironman movies that came out, and the average length of the movies was μ = 127 minutes. Does this average contradict the confidence interval? Explain why.

Answer 1