Company wants to estimate the mean amount of time that the audience spends listening to radio daily ...

1. if xbar = 85, standard deviation = 8, and n =64, Construct a 95% confidence interval estimate for the population mean u

2. Company wants to estimate the mean amount of time that the audience spends listening to radio daily. The standard deviation is estimated as 45 minutes
a. What sample size is needed if the agency wants to be 90% confident of being correct within +/- 5 minutes?
b. If 99% confidence is desired, how many listeners need to be selected?