STAT2401 Lecture Week 6: Analysis of Experiments
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What is the main purpose of diagnostic checking in regression analysis?

  • To generate predictions using the regression model
  • To determine the statistical significance of the slope
  • To estimate the coefficients of the population regression line
  • To validate the regression model and check its assumptions (correct)
  • What is the role of residuals in regression analysis?

  • To test the statistical significance of the slope
  • To estimate the population regression line
  • To standardize the data
  • To estimate the deviations from the population regression line (correct)
  • Why do we need to check the conditions for regression inference?

  • To test the statistical significance of the slope
  • To generate predictions using the regression model
  • To ensure that the regression model is a valid model (correct)
  • To estimate the coefficients of the population regression line
  • What is the purpose of plotting standardized residuals?

    <p>To validate the regression model and check its assumptions</p> Signup and view all the answers

    What is the primary tool used to validate regression assumptions?

    <p>Plot of standardized residuals</p> Signup and view all the answers

    What is the main goal of Aim 1 in regression analysis?

    <p>To critically assess the regression model</p> Signup and view all the answers

    What is the main purpose of critically assessing the regression model?

    <p>To ensure the model meets the assumptions of linear regression</p> Signup and view all the answers

    What is the primary goal of residual analysis in diagnostic checking?

    <p>To verify the assumption of constant variance</p> Signup and view all the answers

    What is the assumption about the residuals in a simple linear regression model?

    <p>They have a zero mean and are normally distributed</p> Signup and view all the answers

    What is the primary condition for making inferences about the regression model?

    <p>The residuals are normally distributed</p> Signup and view all the answers

    What is the purpose of checking the conditions for regression inference?

    <p>To ensure the results of inference are reliable</p> Signup and view all the answers

    What is the implication of the assumption of independence in a simple linear regression model?

    <p>The scatter about the true line will be Normally distributed</p> Signup and view all the answers

    What does the slight curvature in the Normal probability plot of the residuals suggest?

    <p>The responses may not be Normally distributed about the line at each x-value.</p> Signup and view all the answers

    Why should we not automatically eliminate outliers from the data?

    <p>Because outliers may be due to mistakes in data collection.</p> Signup and view all the answers

    What is the purpose of influence analysis?

    <p>To determine the observations that have an influential effect on the fitted model.</p> Signup and view all the answers

    What is the criteria used to determine if an observation is a leverage point?

    <p>If hi &gt; 4/n, Xi is a leverage point.</p> Signup and view all the answers

    What is the condition for an observation to be considered a candidate for removal from the model?

    <p>If Di &gt; 4/n-2.</p> Signup and view all the answers

    What is the purpose of using multiple criteria, such as the hat matrix elements, Studentized deleted residuals, and Cook's distance statistic, in influence analysis?

    <p>To ensure that only when all three criteria provide consistent results, an observation should be removed.</p> Signup and view all the answers

    What is the primary purpose of the influence.measures function in R?

    <p>To explore measures of leverage and Cook's distance</p> Signup and view all the answers

    What is a bad leverage point?

    <p>A point whose standardized residual falls outside the interval from –2 to 2</p> Signup and view all the answers

    What is the purpose of the smoothing red curves in the plot(prod.lm) output in R?

    <p>To help identify patterns</p> Signup and view all the answers

    What is an outlier in the context of regression analysis?

    <p>A point whose standardized residual falls outside the interval from –2 to 2</p> Signup and view all the answers

    What is the characteristic of a good leverage point?

    <p>Its standardized residual falls inside the interval from –4 to 4 for large sample size</p> Signup and view all the answers

    What is the condition for normality to be satisfied in a regression analysis?

    <p>The data should have a fairly constant spread</p> Signup and view all the answers

    What is the primary characteristic of a US Treasury bond that makes it a safe investment?

    <p>Government backing</p> Signup and view all the answers

    What is the effect of a 1% increase in the coupon rate on the mean bid price, according to the fitted model?

    <p>$3.07 increase</p> Signup and view all the answers

    What is the purpose of plotting standardized residuals?

    <p>To identify influential points</p> Signup and view all the answers

    Why are the three points on the left in the plot of the data dragging the least squares line away from the bulk of the points?

    <p>They have high leverage</p> Signup and view all the answers

    What is the recommended approach to deal with influential points in the data?

    <p>Remove them and re-fit the model</p> Signup and view all the answers

    What is the interval estimate for the slope of the least squares line?

    <p>(2.44, 3.69)</p> Signup and view all the answers

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