Ch 12 Answers - Chapter 12 Bivariate Regression 12.1 H : =...

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Unformatted text preview: Chapter 12 Bivariate Regression 12.1 H : = 0 versus H 1 : 0 for a two-tailed test. Summary Table Sample df r t t r Decision a 18 .45 2.138 2.101 .444 Reject b 28 .35 1.977 1.701 .306 Reject c 5 .6 1.677 2.015 .669 Fail to Reject d 59 .3 2.416 2.39 .297 Reject 12.2 a. The scatter plot shows a positive correlation between hours worked and weekly pay. b. Hours Worked (X) Weekly Pay (Y) 2 ( ) i x x- 2 ( ) i y y- ( )( ) i i x x y y-- 10 93 100 7056 840 15 171 25 36 30 20 204 729 20 156 441 35 261 225 7056 1260 20 177 350 15318 2130 x y SSxx SSyy SSxy 2130 .9199 350 15318 r = = c . t .025 = 3.182 d . 2 5 2 .9199 4.063 1 (.9199) t- = =- . We reject the null hypothesis of zero correlation. e. p-value = .0269. 110 12.3 a. The scatter plot shows a negative correlation between operators and wait time. b. Operators (X) Wait (Y) 2 ( ) i x x- 2 ( ) i y y- ( )( ) i i x x y y-- 4 385 4 1444 76 5 335 1 144 12 6 383 1296 7 344 1 9 3 8 288 4 3481 118 6 347 10 6374 185 x y SSxx SSyy SSxy 185 .7328 10 6374 r- = = - c . t .025 = 3.183 d . 2 5 2 .7328 1.865 1 ( .7328) t- = - = -- - . We fail to reject the null hypothesis of zero correlation. e. p-value = .159. 12.4 a. The scatter plot shows little correlation between age and amount spent. b. r calculated = .292 c. t .025 = 2.306 d. 2 10 2 .292 .864 1 ( .292) t- = - = -- - e. critical 2 2.306 .632 2.306 10 2 r = = +- . f. Because r calculated (.292) > .632, we fail to reject the null hypothesis of zero correlation. 111 12.5 a. The scatter plot shows a positive correlation between returns from last year and returns from this year. b. r calculated = .5313 c. t .025 = 2.131 d. 2 17 2 .5313 2.429 1 (.5313) t- = =- e. critical 2 2.131 .482 2.131 17 2 r = = +- f. Because r calculated (.5313) > .482, we reject the null hypothesis of zero correlation. 12.6 a. The scatter plot shows a positive correlation between orders and ship cost. b. r calculated = .820 c. t .025 = 2.228 d. 2 12 2 .820 4.530 1 (.820) t- = =- e. critical 2 2.228 .576 2.228 12 2 r = = +- f. Because r calculated (.820) > .576, we reject the null hypothesis of zero correlation. 12.7 a. Correlation Matrix 1-Year 10-Year 1-Year 1.000 3-Year-.095 5-Year .014 10-Year .341 1.000 12 sample size .576 critical value .05 (two-tail) .708 critical value .01 (two-tail) d. There were positive correlations between years 3 and 5 and years 5 and 10. Higher returns in Year 3 lead to higher returns in Year 5 and also in Year 10. 12.8 a. An increase in the price of $1, reduces its expected sales by 37.5 units. b. Sales = 842 (20)*37.5 = 92 c. From a practical point of view no. A zero price is unrealistic....
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This note was uploaded on 12/13/2010 for the course LEEDS BCOR 1020 taught by Professor Heatheradams during the Spring '08 term at Colorado.

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Ch 12 Answers - Chapter 12 Bivariate Regression 12.1 H : =...

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