# 420Hw07ans - STAT 420(due Friday October 17 by 3:00 p.m...

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STAT 420 Fall 2008 Homework #7 (due Friday, October 17, by 3:00 p.m.) From the textbook: 5.7 a) x y x x - ( ) y y - ( ) 2 x x - ( ) ( ) y y x x - - ( ) 2 y y - 10 15 0 3 0 0 9 5 9 –5 –3 25 15 9 7 3 –3 –9 9 27 81 19 25 9 13 81 117 169 11 7 1 –5 1 -5 25 8 13 –2 1 4 -2 1 60 72 0 0 120 152 294 6 60 = = n x x = 10 6 72 = = n y y = 12 ( ) ( ) ( ) 15 19 120 152 2 ˆ = = & - & - - = x x y y x x 1.266667 . OR x y x x - ( ) 2 x x - ( ) y x x - 10 15 0 0 0 5 9 –5 25 –45 7 3 –3 9 –9 19 25 9 81 225 11 7 1 1 7 8 13 –2 4 –26 60 72 0 120 152 ( ) ( ) 15 19 120 152 2 ˆ = = & - & - = x x y x x 1.266667 .

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OR x y x 2 x y y 2 10 15 100 150 225 5 9 25 45 81 7 3 49 21 9 19 25 361 475 625 11 7 121 77 49 8 13 64 104 169 60 72 720 872 1158 ( )( ) ( ) 15 19 120 152 60 6 1 720 72 60 6 1 872 1 1 2 2 2 ˆ = = - - = = & - & - x n x y x n y x 1.266667 . x y ˆ ± ˆ - = = 12 – 1.266667 10 = 0.66667 . The least-squares regression line: y ˆ = 1.266667 x – 0.66667. OR > X <- c(10,5,7,19,11,8) > Y <- c(15,9,3,25,7,13) > fit <- lm(Y~X) > summary(fit) Call: lm(formula = Y ~ X) Residuals: 1 2 3 4 5 6 3.000 3.333 -5.200 1.600 -6.267 3.533 Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) -0.6667 5.0365 -0.132 0.9011 X 1.2667 0.4598 2.755 0.0511 . ---
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420Hw07ans - STAT 420(due Friday October 17 by 3:00 p.m...

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