A sample of 150 calls to a customer help line

A sample of 150 calls to a customer help line during one week found that callers were kept waiting on average for 16 minutes with s = 8.,(a) Find the margin of error for this result if we use a 95% confidence interval for the length of time all customers during this period are kept waiting.,(b) Interpret for management the margin of error.,(c) If we only need to be 90% confident, does the confidence interval become wider or narrower?,(d) Find the 90% confidence interval.