A sample of 150 calls to a customer help line for one week found that callers were kept waiting on average of 16

minutes with standard deviation of 3.8 minutes.

Q1. Calculate a 90% confidence interval for the true average length of time customers spent waiting

A. (14.234, 16.883) B. (15.034, 16.985) C. (15.486, 16.514) D. (15.387, 16.613)

Q2 . What sample size will be required for you to be able to compute a 95% confidence interval for the true mean

to within 0.45 minutes assuming the true standard deviation of waiting time is 3.8 minutes?

A. 273 B. 150 C. 272 D. 274