The owner of a rapidly growing computer store tried to explain the increase in biweekly sales of computer software, using four explanatory variables: number of titles displayed, display footage, current customer base of Windows- based computers, and current customer base of Mac computers. The data are given below for the 52 biweekly sales periods as follows: biweek, soft-ware sales, number of titles displayed, display footage, Windows- based customers, and Mac based customers.

a. Before doing the calculations, consider the economics of the situation, and state what sign you would expect for each of the partial slopes.
b. Obtain a multiple regression equation with sales as the dependent variable and all other variables as independent. Does each partial slope have the sign you expected in part (a)?
c. Calculate a 95% confidence interval for the coefficient of the titles variable. The computer output should contain the calculated standard error for this coefficient. Does the interval include 0 as a plausible value?

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Biweek Sl Titles Footage Windows Mac 179 197 154 166 184 86.7 86.0122 76.6 87.6 90.4 Biweek Sl Titles 91.7 115 80.7 110 85.2 113 106.6 129 91.4 124 Windows Mac 168 153 182 206 183 continued) 116 362 318 349 330 6 112 116 122 70 79 337 354 72 93 82 10 381 70 2 2 2 2 2 2 2 996 75 26 197 ns 996 74 202 194 194 742135 642445 769 300 soi ATI // 4% aya $12 500 sop sir 999 apa $15 4% $10 4% $30 STA 996 5 4445 55445 0 1 1811754877640 2 0 0 1 4 8 2 Sa-12 2 2 2 2 2 1 1 1 3 14 1 5 3 4 3 2 1 1 41 3 3 3 3 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 31106 13 Ma-20 20 20 17 2 2 2 22 18 21 22 24 2 2 2 2 2 2 2 2 7 374744853424 3444 42 4444 42 ww 85 96 85 78 101 92 99 96万88 80 88 91 89 84 98 99 103 91 98 92 0 066 26 4 6 2 6 7 293181 772 678901