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STAT 462 - HW 2 Solution Key

# STAT 462 - HW 2 Solution Key - Stat 462 Spring 2008...

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Stat 462, Spring 2008 Homework 2 Solution key Due February 8, 2008 Prepared by: Esra Kurum STAT 462 HOMEWORK 2 SOLUTION KEY 1.20 a) Regression Analysis: Y versus X The regression equation is Y = - 0.58 + 15.0 X Predictor Coef SE Coef T P Constant -0.580 2.804 -0.21 0.837 X 15.0352 0.4831 31.12 0.000 S = 8.91351 R-Sq = 95.7% R-Sq(adj) = 95.7% b) 10 8 6 4 2 0 160 140 120 100 80 60 40 20 0 X Y S 8.91351 R-Sq 95.7% R-Sq(adj) 95.7% Fitted Line Plot Y =  - 0.580 + 15.04 X Since the R-square (95.7 %) is large we can say that this is a good fit.

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Stat 462, Spring 2008 Homework 2 Solution key Due February 8, 2008 Prepared by: Esra Kurum c) Since the scope of model in this data set doesn’t cover x=0, b 0 doesn’t have any meaning. However, when the scope of the model includes x=0 then b 0 gives the mean of the probability distribution of Y at x=0. d) E(Y) =-0.58+15X then at x=5 E(Y)= 74.42 1.22 a) Regression Analysis: Y versus X The regression equation is Y = 169 + 2.03 X Predictor Coef SE Coef T P Constant 168.600 2.657 63.45 0.000 X 2.03437 0.09039 22.51 0.000 S = 3.23403 R-Sq = 97.3% R-Sq(adj) = 97.1% 40 35 30 25 20 15 260 250 240 230 220 210 200 190 X Y S 3.23403 R-Sq 97.3% R-Sq(adj) 97.1% Fitted Line Plot Y =  168.6 + 2.034 X Since R-square is large (97.3%), we can say that this is a good fit.
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