(A) The scatterplot looks linear and there is no curve in the residual plot, so a significance test is
appropriate.
(B) The scatterplot has a curve in it, so a significance test is not appropriate.
(C) There is a curve in the residual plot, so a significance test is not appropriate.
(D) The variation in the residuals is not uniform, so a significance test is not appropriate.
(E) The univariate plot of the residuals is strongly skewed, so a significance test is not appropriate.
When constructing a confidence interval for the slope of a regression line for a data set with n points,
which is the correct consideration for the critical value?
(A) Because the sampling distribution of the slope is approximately normal, z should be used as the
critical value.
(B) Because the standard deviation of the slope is unknown, t with n degrees of freedom should be
used as the critical value.
(C) Because the standard deviation of the slope is unknown, t with n – 1 degrees of freedom should
be used as the critical value.
(D) Because the standard deviation of the slope is unknown, t with n – 2 degrees of freedom should
be used as the critical value.
(E) Because the sample size is already considered in the formula for the standard error of the slope,
no critical value is needed.
- A teacher wondered if there was a relationship between students’ ACT math scores and their ACT
reading scores. He selected a random sample of students who took the ACT, created a scatterplot,
and saw that there appears to be a positive linear relationship. A significance test for the slope for
predicting the ACT math score from the ACT reading score showed a P- value very close to 0.
Which of the following is a valid conclusion?
(A) Students who have higher ACT reading scores tend to have higher ACT math scores.
(B) To improve their ACT math scores, students should work to improve their ACT reading scores.
(C) To improve their ACT reading scores, students should work to improve their ACT math scores.
(D) There is strong evidence that a higher ACT reading score will result in a higher ACT math
score.
(E) There is some evidence that a higher ACT reading score will result in a higher ACT math score. - The following table shows the number of cylinders in the engine and the gas mileage for a random
sample of automobiles by a certain manufacturer. Assume all conditions for inference are met.