Name:    CP Statistics - Chapter 3: Examining Linear Relationships

Multiple Choice
Identify the choice that best completes the statement or answers the question.

1.

Suppose the following information was collected, where X = diameter of tree trunk in inches, and Y = tree height in feet.

 X 4 2 8 6 10 6 Y 8 4 18 22 30 8

If the LSRL equation is y = –3.6 + 3.1x, what is your estimate of the average height of all trees having a trunk diameter of 7 inches?
 a. 18.1 b. 19.1 c. 20.1 d. 21.1

2.

A copy machine dealer has data on the number x of copy machines at each of 89 customer locations and the number y of service calls in a month at each location.  Summary calculations give = 8.4, Sx = 2.1, = 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?
 a. 0.86 b. 1.56 c. 0.48 d. None of these

3.

There is a linear relationship between the number of chirps made by the striped ground cricket and the air temperature.  A least squares fit of some data collected by a biologist gives the model = 25.2 + 3.3x,  where x is the number of chirps per minute and is the estimated temperature in degrees Fahrenheit.  What is the estimated increase in temperature that corresponds to an increase in 1 chirp per minute?
 a. 1.0 °F b. 3.3 °F c. 25.2 °F d. 28.5 °F

4.

A set of data relates the amount of annual salary raise and the performance rating.  The least squares regression equation is = 1,400 + 2,000x   where y is the estimated raise and x is the performance rating.  Which of the following statements is not correct?
 a. The expected salary for a performance rating of 0 is \$1,400. b. For each increase of one point in performance rating, the raise will increase on average by \$2,000. c. The correlation for of these two variables is positive. d. All of the above are true.

5.

Below is a scatterplot of the calories and sodium content (in milligrams) of several brands of meat hot dogs. The least-squares regression line has been drawn on the plot. Based on the least-squares regression line in this scatterplot, one would predict that a hot dog containing 100 calories would have a sodium content (in milligrams) of about
 a. 70 b. 350 c. 400 d. 550

Scenario 3-3

Consider the following scatterplot, which describes the relationship between stopping distance (in feet) and air temperature (in degrees Centigrade) for a certain 2,000-pound car travelling 40 mph. 6.

Use Scenario 3-3. The correlation between temperature and stopping distance
 a. is approximately 0.9. b. is approximately 0.6. c. is approximately 0.0. d. is approximately -0.6.

7.

Which of the following has a correlation that is closest to 0?
 a. c. b. d. 8.

Which of the following is NOT true about the correlation coefficient r?
 a. b. When the slope of the data is negative, the correlation r will be negative c. Whenever all the data lie on a perfectly straight line, the correlation r will always be equal to +1.0 d. Correlation is greatly affected by outliers

The table below shows the temperature of a pot of water as it is being heated on a stove.

 Time (min), x 1 2 3 4 5 Temp (ºF), y 76 80 84 88 92

9.

What is the predicted temperature of the water after 8 minutes?
 a. 100º b. 104º c. 108º d. 112º

10.

What was the temperature of the water before it was heated?
 a. 70º b. 72º c. 74º d. 76º