Problem 3: A telephone company claims that the mean duration of all long-distance

phone calls made by its residential customers is 10 min- utes. A random sample of 25

long-distance calls made by its residential customers taken from the records of this

company showed that the mean duration of calls for this sample is 9.20 minutes with

standard deviation of 2.80 minutes. Using these sample information, investigate the

company's claims at 1% level of significance. Find the p-value and interpret it.