Over the past decade or so, Starbucks has grown quite rapidly. As they add stores and increase the number of drinks, their sales revenue increses. In reflecting about this growth, think about some other variables that might be related to the increase in starbucks sales revenues. Some data for the past seven years on the number of starbucks stores (worldwide), approximate sales revenue (in millions), number of different drinks sold, and average weekly earnings of U.S production workers are given here. Most figures are approximate. Develop a multiple regression model to predict sales revenue by the number of drinks sold, number of stores, and average weekly earnings. How strong is the model? What are the key predictions, if any? How might this analysis help Starbucks managment in attempting to determine what drives sales revenues?

Sales Year Revenue # of stores # of Drinks Avg weekly earnings
1 400 676 15 386
2 700 1015 15 394
3 1000 1412 18 407
4 1350 1886 22 425
5 1650 2135 27 442
6 2200 3300 27 457
7 2600 4709 30 474