Question: The National Association of Realtors (NAR) Existing Home Sales Series provides a measurement of the residential real estate market. On or about the 25th of each month, NAR releases statistics on sales and prices of condos and co-ops, in addition to existing single family homes, for the nation and the four regions. The data presented here indicate the number of (in thousands) existing-home sales as well as condo/co-op sales:
a. Construct the regression equation that would predict the number of condo/co-op sales using the number of single-family sales.
b. One might conjecture that these two markets (single-family sales and condo/co-op sales) would be competing for the same audience. Therefore, we would expect that as the number of single family sales increases, the number of condo/co-op sales would decrease. Conduct a hypothesis test to determine this using a significance level of 0.05.
c. Provide a prediction interval for the number of condo/co-op sales when the number of single family sales is 6,000 (thousands). Use a confidence level of 95%.