A real estate agent has received data on 150 houses that were recently sold in a suburban community. Included in this data set are observations for each 6f the following variables: the appraised value of each house (in thousands of dollars), the selling price of each house (in thousands of dollars), the size of each house (in hundreds of square feet), and the number of bedrooms in each house. The data are in the file P2_7.XLS.

a. Suppose that this real estate agent wishes to examine a representative subset of these 150 houses that has been stratified by the number of bedrooms. Use Excel to assist her by finding such a stratified sample of size 15 with proportional sample sizes.

b. Explain how the real estate agent could apply cluster sampling in selecting a sample of size 15 from this frame. What are the advantages and disadvantages of employing cluster sampling in this case?