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:

  1. 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 t=0.64t = -0.64). This suggests that Time is not statistically significant at this level.
  2. Comparing Adjusted R2R^2 Values:

    • Model B has an Adjusted R2R^2 of 0.7388.
    • Model C (which excludes Time) has an Adjusted R2R^2 of 0.7421.

    The adjusted R2R^2 for Model C is slightly higher than that for Model B. Since adjusted R2R^2 accounts for the number of predictors in the model and Model C has a higher adjusted R2R^2, this suggests that Model C may provide a better fit than Model B.

Given this information, let’s analyze the options:

  1. Yes, removing Time from Model B results in Model C, which has a higher adjusted R2R^2.

    • This is correct because Model C has a higher adjusted R2R^2 than Model B, indicating it might be a better model after removing the insignificant variable.
  2. No, Model B has the highest R2R^2, so it should be used for making predictions.

    • This is incorrect because although Model B has the highest R2R^2, the adjusted R2R^2 is lower than Model C. The adjusted R2R^2 is a more appropriate measure when comparing models with different numbers of predictors.
  3. Yes, Time should be deleted because we could not prove its significance even for α=0.10\alpha = 0.10.

    • This is correct because Time is not significant at the 10% level, suggesting that it doesn’t contribute significantly to the model.
  4. No, removing Time from Model B results in Model C, which has a lower R2R^2.

    • This is incorrect because the question should consider adjusted R2R^2, not just R2R^2. Model C actually has a higher adjusted R2R^2.

Conclusion: The most appropriate answers are:

  1. Yes, removing Time from Model B results in Model C which has a higher adjusted R2R^2.
  2. Yes, Time should be deleted because we could not prove its significance even for α=0.10\alpha = 0.10.

Either of these options would be correct.

Would you like more details or have any questions?

Related Questions:

  1. What is the interpretation of the coefficient for Prime in Model C?
  2. How does the inclusion of interaction terms affect the interpretation of regression models?
  3. What is the significance of using adjusted R2R^2 over regular R2R^2 when comparing models?
  4. Why is it important to consider the significance level when testing individual predictors?
  5. How does the t-statistic relate to the p-value in hypothesis testing?
  6. What are the implications of multicollinearity in regression models?
  7. How would you interpret the interaction term Time×Prime\text{Time} \times \text{Prime} in Model B?
  8. What are the consequences of overfitting in regression models?

Tip: Always check both the R2R^2 and adjusted R2R^2 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