Question: As part of their business promotional package, the Milwaukee Chamber of Commerce would like an estimate of the mean cost per month to lease a one-bedroom apartment. The mean cost per month for a random sample of 40 apartments currently available for lease was $900. The population is normal with standard deviation of $50.

1. Develop a 99% confidence interval for the population mean.
2. Develop a 95% confidence interval for the population mean.
3. What impact have you noticed on the confidence interval. Write a reason.
4. Write the reason of using z- or t-distribution.