Exam 5: Hypothesis Testing in Linear Regression Analysis

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When using the p-value method for hypothesis testing,if the calculated p-value is smaller than the chosen significance level,then you should

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Why are each of the individual simple linear regression model assumptions important? Explain.

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Assumption 1:If the model is not correctly specified then the estimates based on it will not be meaningful or true.

Assumption 2:If the data is not collected through random sampling then a model that is specified conditional on the observations not being related to each other then the estimated coefficients will be wrong.

Assumption 3:If the independent variable does not vary then β^1\hat { \beta } _ { 1 }
is not defined and therefore an estimate cannot be derived.

Assumption 4:If the average value of the error term is not equal to zero then the estimates on average will be wrong on average.

Assumption 5:If the error term is related to the independent variables,then if the independent variable increases by one unit then the error term will increase as well,therefore not allowing for a measurement of how the independent variable affects the dependent variable holding other factors constant (because the error term changed as well).

Assumption 6:If the variance of the error term is not constant then OLS,that treat all observations the same,is not the most preferred method to estimate the regression model.

A counselor working with teenagers is interested in the relationship between anxiety and depression.The counselor administers a depression and anxiety test to each teenager.The scores obtained from the administration of the two inventories are given below. Anxiety Depression 22 16 12 8 68 33 10 6 5 5 53 24 44 18 37 17 0 2 21 14 64 31 33 17 55 30 18 13 3 3 4 4 11 7 13 9 7 5 The summary statistics are Anxiety Depression Sample mean 25.2632 13.7895 Standard deviation 21.9895 9.8464 i=119(x1xˉ)(yiyˉ)=3828.0526\sum_{i=1}^{19}\left(x_{1}-\bar{x}\right)\left(y_{i}- \bar{y}\right)=3828.0526 If an individual had an anxiety score of 40,what is a 95% confidence interval for the mean predicted value?

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depress^ion=2.6782+0.4398 anxiety =2.6782+(0.4398)(40)=20.27 dep\widehat {ress}ion = 2.6782 + 0.4398 \cdot \text { anxiety } = 2.6782 + ( 0.4398 ) \cdot ( 40 ) = 20.27
This means if a person scores 40 on the anxiety test they are predicted to score 20.27 on the depression test.

critical value = 2.11

standard error = 0.5298

95% confidence interval for the mean value is (19.1531,21.2889).

A sampling distribution is

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The t-statistic for the individual significance of the estimated slope coefficient β^1\hat { \beta } _ { 1 } Is

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Figure: Suppose you regress U.S.annual real GDP ($ billions)on U.S.annual real defense expenditures ($ millions)and that you get the following results. SUMMARY OUTPUT Regvessiait Statistics Muatiple R. 0.523337059 R Sqare 0.273881677 Adjusted R Square 0.263508558 Standard Error 3201.551247 Obsenvations 72 ANOVA of SS MS F Siguffecance F Regressice 1 270629128.2 270629128.2 26.4030211 2.39636-06 Residual 70 717495127 10249930.39 Total 71 988124255.3 Coeffieients Staudard Errar t Stat P-value Lower 95\% Upper 95\%6 linercept 1273.293919 979.7967762 1.299548998 0.198019186 -680.8491085 3227.436946 Real Defense Expesdtures (milions) 0.013659042 0.002658235 5.138387013 2.39636-06 0.008357359 0.018960725  Figure 5.1\text { Figure } 5.1 -Based on the Excel output in Figure 5.1,you should conclude that

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What is the intuition behind the critical-value method of hypothesis testing? Explain.

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The logic behind the F-test for the overall significance of the estimated sample regression function is that if the estimated sample regression function explains a significant amount of the variation in the dependent variable,then

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The logic behind the t-test for the individual significance of the estimated slope coefficient β^1\hat { \beta } _ { 1 } Is that if the estimated slope coefficient is likely to be different from 0,then

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What is the intuition behind the confidence interval method of hypothesis testing? Explain.

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The p-value method for hypothesis testing relies on the fact that

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Figure Suppose you regress obesity rates for the 50 states and the District of Columbia on the percentage of adults who have earned a Bachelor's degree and that you get the following results. SUMMARY OUTPUT Regression Staristies Multple R. 0.755633848 R. Square 0.570982512 Adjasted R. Square 0.562227053 Standard Erroe 2.233627219 Observations 51  ANOVA \text { ANOVA } df SS MS F Significance F Regression 1 325,3608375 325.3608375 65.21445826 1.46476-10 Residual 49 244.465437 4.989090551 Total 50 569.8262745 Coefficients Standard Ewor t Stat P-value Lower 95\%6 Ueper 9596 Intercept 40.59256588 1.597069735 25.41690259 7.09161-30 37.38313415 43.80199761 Percent Aduhs with Bachelor's Deryee -0.465887223 0.057691105 -8.075546932 1.46476-10 -0.581821836 -0.34995261  Figure 5.2\text { Figure } 5.2 -Based on the Excel output in Figure 5.2,you should conclude that the estimated sample regression function is

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What is a sampling distribution? Why is it important? Explain.

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What is the intuition behind the p-value method of hypothesis testing? Explain.

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Figure: Suppose you regress U.S.annual real GDP ($ billions)on U.S.annual real defense expenditures ($ millions)and that you get the following results. SUMMARY OUTPUT Regvessiait Statistics Muatiple R. 0.523337059 R Sqare 0.273881677 Adjusted R Square 0.263508558 Standard Error 3201.551247 Obsenvations 72 ANOVA of SS MS F Siguffecance F Regressice 1 270629128.2 270629128.2 26.4030211 2.39636-06 Residual 70 717495127 10249930.39 Total 71 988124255.3 Coeffieients Staudard Errar t Stat P-value Lower 95\% Upper 95\%6 linercept 1273.293919 979.7967762 1.299548998 0.198019186 -680.8491085 3227.436946 Real Defense Expesdtures (milions) 0.013659042 0.002658235 5.138387013 2.39636-06 0.008357359 0.018960725  Figure 5.1\text { Figure } 5.1 -Based on the Excel output in Figure 5.1,you should conclude that the estimated sample regression function is

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Why is hypothesis testing is necessary? Explain.

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A confidence interval is constructed

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When using the critical value method for hypothesis testing,if the value of the test statistic is less than the critical value,then you should

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If we find that it is unlikely to observe the sample statistic that is actually observed if the null hypothesis is true,then we should

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A standard error is

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