1- For a population data set, sigma= 13.3. How large a sample should be selected so that the margin of error of estimate for a 99% confidence interval for u is ?

Round your answer up to the nearest whole number. n=?

2- A city planner wants to estimate the average monthly residential water usage in the city. He selected a random sample of 43 households from the city, which gave the mean water usage to be 3410.70 gallons over a one-month period. Based on earlier data, the population standard deviation of the monthly residential water usage in this city is 387.30 gallons. Make a 97% confidence interval for the average monthly residential water usage for all households in this city.

Round your answers to two decimal places.

3- A researcher wants to determine a 99% confidence interval for the mean number of hours that adults spend per week doing community service. How large a sample should the researcher select so that the estimate is within 1.6 hours of the population mean? Assume that the standard deviation for time spent per week doing community service by all adults is 3 hours.

Round your answer up to the nearest whole number.