Explain with details please. df pdf (1).pdf ktop/New%20folder/pdf%20(1),pr 21. R

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Explain with details please.

df pdf (1).pdf ktop/New%20folder/pdf%20(1),pr 21. Refer to Scenario: Exam Grades-Part 2. You run two new OLS specifications in R. (i) Grade= 0 + 1(Hours) + 2(SAT0+ summary Im(Grade Hours + SAT, data-Export5)) Call: m(formula = Grade-Hours + SAT, data-ExportS) Residuals: Min -15.6640 -3.7476 0.5606 4.1837 14.1397 10 Median 3QMax Coefficients: Estimate Std. Error tvalue Pre lt) (Intercept) 22.52703 10.16500 2.2160.031669 Hours SAT 3.11552 0.437227.126 5.9e-09 0.03300 0.00802 4.114 0.000159* Signif.codes: 0.001 0.01 0.05 0.11 Residual standard errors 6.367 on 46 degrees of freedom ultiple R-squared: 0.6189, Adjusted R-squared: 0.6023 statistic: 37.35 on 2 and 46 DF. p-value: 2.31le 10 17 Oo

Explanation / Answer

21.

In the presence of the independent variable ACT, both SAT and ACT are not significant predictors of the response variable Grade. However, in the absence of ACT variable, SAT is a significant predictor of Grade. So there is multicollinearity.

There is also a variable Hours which may be correlated with ACT or SAT.

Hence, there is imperfect multicollinearity.

Hence the answer is - B

22.

We cannot include all the variables Bronx, Brooklyn, Manhattan, Queens and Staten in the model. As they will be redundant. So if we include all these variables in the model, that model would violate the assumptions and would thus be inappropriate.

Hence the answer is - D

27.

The difference between the original OLS model and this new specification is the addition of an interaction term.

However the p-value of the interaction term in the model is 0.63124 which is not significant.

So this addition was probably not necessary.

Hence the answer is - D

28.

If b1 and b2 are both statistically significant and > 0

Then the relation between Hours and Grade is positive.

d(Grades)/d(Hours) = b1 + 2 b2 Hours

d2(Grades)/d(Hours)2 = 2 b2 > 0

So the relation between Grades and Hours is Convex.

Hence the answer is - A

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