End of Section Problem 14.1 (Essay)
Use the following data to develop a quadratic model to predict
y from x. Develop a simple regression model from
the data and compare the results of the two models. Does the
quadratic model seem to provide any better predictability? Why or
why not?
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simple
SUMMARY OUTPUT | ||||||
Regression Statistics | ||||||
Multiple R | 0.985100338 | |||||
R Square | 0.970422677 | |||||
Adjusted R Square | 0.966197345 | |||||
Standard Error | 27.26526302 | |||||
Observations | 9 | |||||
ANOVA | ||||||
df | SS | MS | F | Significance F | ||
Regression | 1 | 170733.7936 | 170733.7936 | 229.6677983 | 1.31023E-06 | |
Residual | 7 | 5203.761973 | 743.3945676 | |||
Total | 8 | 175937.5556 | ||||
Coefficients | Standard Error | t Stat | P-value | Lower 95% | Upper 95% | |
Intercept | -147.269636 | 22.77583041 | -6.466049026 | 0.000344996 | -201.1259169 | -93.41335509 |
x | 27.12787356 | 1.790052214 | 15.15479456 | 1.31023E-06 | 22.89507269 | 31.36067444 |
quadratic
SUMMARY OUTPUT | ||||||
Regression Statistics | ||||||
Multiple R | 0.997418275 | |||||
R Square | 0.994843215 | |||||
Adjusted R Square | 0.993124286 | |||||
Standard Error | 12.29683009 | |||||
Observations | 9 | |||||
ANOVA | ||||||
df | SS | MS | F | Significance F | ||
Regression | 2 | 175030.2834 | 87515.14169 | 578.757798 | 1.37131E-07 | |
Residual | 6 | 907.2721818 | 151.2120303 | |||
Total | 8 | 175937.5556 | ||||
Coefficients | Standard Error | t Stat | P-value | Lower 95% | Upper 95% | |
Intercept | -22.01123636 | 25.64570955 | -0.85828143 | 0.423691879 | -84.76402698 | 40.74155426 |
x | 3.384864819 | 4.526796386 | 0.747739578 | 0.482883408 | -7.691806904 | 14.46153654 |
x^2 | 0.937330351 | 0.175844569 | 5.330448108 | 0.001777382 | 0.507054191 | 1.367606511 |
R^2 for linear = 0.970422677
R^2 for quadratic model = 0.994843215
since R^2 for quadratic is more that R^2 for linear
Quadratic model is better
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