Chapter_7_Recommended_Homework_Solutions

Chapter_7_Recommended_Homework_Solutions - Chapter 7...

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Unformatted text preview: Chapter 7 Recommended Homework Solutions 7-8. a) Estimated Effects and Coefficients for charge Term Coef StDev Coef T P Constant -1.000 0.4462 -2.24 0.055 method -2.797 0.4462 -6.27 0.000 position -0.640 0.4462 -1.43 0.189 method*position -0.610 0.4462 -1.37 0.209 b) 0.0-2.5-5.0 position Mean Interaction Plot for charge The interaction plot does not indicate a significant interaction between Method and Position. c) The t-ratios are given in the output shown in part a. The t-ratios indicate that only Method is significant at the = 0.05 level. d) The 95% confidence intervals are given by effect estimate 2(s.e.(effect)) where s.e.(effect) = 2[s.e.(coefficient)]. The s.e.(coefficient) is given in the Minitab output of part a. Method: s.e.(effect) = 2(0.4462) = 0.8924 Approximate 95% confidence interval on the the effect of Method:- 5.593 2(0.8924) (- 7.38, - 0.3.81) Position: s.e.(effect) = 2(0.4462) = 0.8924 Approximate 95% confidence interval for the effect of Position:- 1.28 2(0.8924) (- 3.065, 0.505) Method*Position: s.e.(effect) = 2(0.4462) = 0.8924 Approximate 95% confidence interval for the effect of Method*Position:- 1.22 2(0.8924) (- 3.005, 0.565) e) The regression equation is charge = - 1.00 - 2.80 method - 0.640 position - 0.610 meth*pos Predictor Coef StDev T P Constant -1.0000 0.4462 -2.24 0.055 method -2.7967 0.4462 -6.27 0.000 position -0.6400 0.4462 -1.43 0.189 meth*pos -0.6100 0.4462 -1.37 0.209 Based on the regression analysis, only Method appears to be the significant factor. This result is equivalent to that obtained in part c. The regression analysis and final model are The regression equation is charge = - 1.00 - 2.80 method Predictor Coef StDev T P Constant -1.0000 0.4873 -2.05 0.067 method -2.7967 0.4873 -5.74 0.000 S = 1.688 R-Sq = 76.7% R-Sq(adj) = 74.4% Analysis of Variance Source DF SS MS F P Regression 1 93.856 93.856 32.94 0.000 Error 10 28.490 2.849 Total 11 122.347 Unusual Observations Obs method charge Fit StDev Fit Residual St Resid...
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Chapter_7_Recommended_Homework_Solutions - Chapter 7...

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