Name: Exam Score: Instructions: This exam covers the material from chapters 4 an

Question

Name: Exam Score: Instructions: This exam covers the material from chapters 4 and 14. Please read each question carefully before you attempt to solve them. Remember that you have to show all of your work clearly in order to get credit. Any problem requiring data will indicate such fact. The exam is closed book. Good luck! Problem 1: Multiple Choice Which of the following statements is true about checking for the constant standard deviation condition? a. If the points of the QQ plot are close to the straight line, then we can conclude the constant standard deviation condition is met b. If the plot of the residuals against time shows no trend, then we can conclude the c. If the residual plot shows a fan shape, then we can conclude the constant standard d. If the residual plot shows no features such as a trend or a fan shape, then we can constant standard deviation condition is met. deviation condition is met conclude the constant standard deviation condition is met. e. None of the above

Explanation / Answer

D) is correct

in which the standard deviation increases with increasing values of the response, are among the most common ways that non-constant random variation occurs in physical science and engineering applications.

Other residual plot shapes besides the horn shape could indicate non-constant standard deviation as well. For example, if the response variable for a data set peaked in the middle of the range of the predictors and was small for extreme values of the predictors, the residuals plotted versus the predictors would look like two horns with the bells facing one another.

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