Chapter 3 AP Stats Review

If bivariate data set A has correlation r = 0.95, and a second bivariate data set B has correlation r = –0.95, then

• a linear model does a better job of describing the relationship between the variables in data set A than in data set B.

• a linear model does a better job of describing the relationship between the variables in data set B than in data set A.

• a linear model is the best description of the relationship between the variables in both data set A and data set B.

• you can’t tell whether either data set is best described by a linear model until you examine the scatterplots.

• a mistake has been made—r cannot be negative.

A copy machine dealer has data on the number of copy machines x at each of 89 customer locations and the number of service calls in a month y at each location. Summary calculations give x̅= 8.4, sx= 2.1, y̅= 14.2, sy= 3.8, and r = 0.86. What is the slope of the least-squares regression line of number of service calls on number of copiers?

• 0.86

• 1.56

• 0.48

• 2.82

• cannot tell from the information given

Suppose we fit a least-squares regression line to a set of data. What is true if a plot of the residuals shows a curved pattern?

• a straight line is not a good model for the data

• the correlation must be 0

• the correlation must be positive

• outliers must be present

• The regression line might or might not be a good model for the data, depending on the extent of the curve.

• no correlation
• undefined correlation
• positive correlation
• negative correlation

Estimate the correlation coefficient.

• r = -0.8

• r = -0.5

• r = 0.5

• r = 0.8

3)

• A

• B

• C

• D

The scatter plot in the figure below shows the GPA of the students of a class versus their commute time. Which of the following statements is true?

• The relationship between GPA and commute time is moderate positive linear.

• The relationship between GPA and commute time is moderate negative linear.

• The scatter plot does not have any outliers.

What is the correlation?

• Negative correlation

• No correlation

• Positive correlation

• Cannot be determined

Which is TRUE?
I.  Random scatter in the residuals indicates a linear model.
II.  If two variables are very strongly associated, then the correlation between them will be near 1 or -1.
III.  Changing the units of measurement for x or y changes the correlation coefficient.

• I only

• II only

• I and II only

• I, II and III

What type of association does this graph have?

• positive 

• negative

• none

• all of the above