A product manager is interested in learning how sensitive sales are to changes in the unit price of a frozen pizza in Toronto, Montreal, Calgary, and Halifax. Data have been provided in the file on both Price and Sales volume every 18 weeks over a period of nearly four years for the four cities (ch18_MCSP_Frozen_Pizza). 

Examine the relationship between Price and Sales for each city. Be sure to discuss the nature and validity of this relationship. Is it linear? Is it negative? Is it significant? Are the conditions of regression met? Some individuals in the product manager’s division suspect that frozen pizza sales are more sensitive to price in some cities than in others. Is there any evidence to suggest that? Write up a short report on what you find. Include 95% confidence intervals for the mean Sales if the Price is $2.50 and discuss how that interval changes if the Price is $3.50.