Examining Residuals for Groups

Multiple Choice

Examining residuals for groups.
-A medical researcher was interested in determining how systolic blood pressure is
Affected by increased exertion during exercise for a sample of cardiac patients. She
Measured the systolic blood pressure of participants in the study as the speed of the
Treadmill on which they were walking was increased. The regression line fit to these data
Was Systolic BP = 97.5 + 12.9 Treadmill Speed, which is significant at = 0.05. The
Α
Residual plot shown below indicates values for smokers and nonsmokers. Which of the
Following statements is true?

A) Smokers have systolic blood pressures higher than what the model predicts.
B) Nonsmokers have systolic blood pressures lower than what the model predicts.
C) The regression model fit to these data should take into account whether a participant is a smoker or not.
D) All of the above.
E) None of the above.