Question: The real estate assessor for a county government wants to study various characteristics of single-family houses in the county. A random sample of 70 houses reveals the following:

? Heated area of the houses (in square feet): ?? = 1,759, S = 380.

? 42 houses have central air-conditioning.

a. Construct a 99% confidence interval estimate for the population mean heated area of the houses.

b. Construct a 95% confidence interval estimate for the population proportion of houses that have central air-conditioning.