Math Problem Statement
Consider the following models A, B, and C:
Model A: Balance = β0 + β1Prime + ε
Model B: Balance = β0 + β1Time + β2Prime + β3Time × Prime + ε
Model C: Balance = β0 + β1Prime + β2Time × Prime + ε,
The regression results obtained for the models are summarized in the following table.
Variable Model A Model B Model C Intercept 88,020 (t = 77.89) 90,269 (t = 24.35) 88,020 (t = 81.19) Time N/A −148 (t = −0.64) N/A Prime −18,000 (t = −11.26) −28,493 (t = −5.36) −26,244 (t = −6.66) Time × Prime N/A 662 (t = 2.03) 514 (t = 2.27) SSE 1,532,480,000 1,369,126,091 1,381,128,299 R2R-squared 0.7254 0.7547 0.7526 Adjusted R2R-squared 0.7198 0.7388 0.7421 Note: The values of relevant test statistics are shown in parentheses below the estimated coefficients.
Suppose that at a 10% significance level, you do not reject the null hypothesis, H0: β1 = 0, when testing the individual significance of Time in Model B. Would you delete Time from Model B?
Multiple Choice
Yes, removing Time from Model B results in Model C which has a higher adjusted R2R-squared.
No, Model B has the highest R2R-squared, so it should be used for making predictions.
Yes, Time should be deleted because we could not prove its significance even for α = 0.10.
No, removing Time from Model B results in Model C which has a with lower R2R-squared.
Solution
The question asks whether Time should be deleted from Model B based on the given significance level and the regression results.
Here’s a breakdown of the relevant information:
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Significance of Time in Model B:
- The p-value associated with the Time coefficient in Model B is not significant at the 10% level (as indicated by ). This suggests that Time is not statistically significant at this level.
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Comparing Adjusted Values:
- Model B has an Adjusted of 0.7388.
- Model C (which excludes Time) has an Adjusted of 0.7421.
The adjusted for Model C is slightly higher than that for Model B. Since adjusted accounts for the number of predictors in the model and Model C has a higher adjusted , this suggests that Model C may provide a better fit than Model B.
Given this information, let’s analyze the options:
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Yes, removing Time from Model B results in Model C, which has a higher adjusted .
- This is correct because Model C has a higher adjusted than Model B, indicating it might be a better model after removing the insignificant variable.
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No, Model B has the highest , so it should be used for making predictions.
- This is incorrect because although Model B has the highest , the adjusted is lower than Model C. The adjusted is a more appropriate measure when comparing models with different numbers of predictors.
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Yes, Time should be deleted because we could not prove its significance even for .
- This is correct because Time is not significant at the 10% level, suggesting that it doesn’t contribute significantly to the model.
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No, removing Time from Model B results in Model C, which has a lower .
- This is incorrect because the question should consider adjusted , not just . Model C actually has a higher adjusted .
Conclusion: The most appropriate answers are:
- Yes, removing Time from Model B results in Model C which has a higher adjusted .
- Yes, Time should be deleted because we could not prove its significance even for .
Either of these options would be correct.
Would you like more details or have any questions?
Related Questions:
- What is the interpretation of the coefficient for Prime in Model C?
- How does the inclusion of interaction terms affect the interpretation of regression models?
- What is the significance of using adjusted over regular when comparing models?
- Why is it important to consider the significance level when testing individual predictors?
- How does the t-statistic relate to the p-value in hypothesis testing?
- What are the implications of multicollinearity in regression models?
- How would you interpret the interaction term in Model B?
- What are the consequences of overfitting in regression models?
Tip: Always check both the and adjusted values, especially when comparing models with different numbers of predictors.
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Math Problem Analysis
Mathematical Concepts
Regression Analysis
Statistical Significance
Adjusted R-squared
Formulas
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Theorems
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Suitable Grade Level
Advanced
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