The management of a supermarket wants to find if there is a relationship between the number of times a specific product is promoted on the intercom system in the store and the number of units of that product sold. To experiment the management selected a product and promoted it on the intercom system for seven days. The following table gives the number of times this product was promoted each day and the number of units sold. Number of Promotions per Day Number of Units Sold per Day (hundreds)
15 11
22 22
42 30
30 26
18 17
12 15
38 23
a) With the number of promotions as an independent variable and the number of units sold as the dependent variable determine the least squares regression line. Give the equation of the line.
b) Compute r and r2. Explain their meaning.
c) Predict the number of units of this product sold on a day with 35 promotions.
d) Construct a 98% confidence interval for \beta .
e) Test at the 1% significant level that \beta is \beta \neq 0.