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a. What is the variance of C?

b. What is the covariance of B and D?

A

B

C

D

A

432.1

B

−

345.1

1033.1

C

19.23

−

543.1

762.4

D

123.81

−

176.4

261.3

283.0

20. What is the correlation between amount of alcohol consumption and the ability

to operate an automobile safely—Negative or positive?

21. Consider the sample data in the table below.

Obs. #

Early

Late

1

3

14

2

4

10

3

7

12

4

5

7

5

7

9

6

6

9

7

7

10

8

6

12

9

2

16

10

1

13

11

2

18

12

4

16

13

3

17

14

5

9

15

2

20

a. Perform an analysis of the descriptive statistics for each data category (Early

and Late).

b. Graph the two series and predict the correlation between Early and Late—

positive or negative?

c. Find the correlation between the two series.

d. Create a histogram for the two series and graph the results.

e. Determine the 99% conﬁdence interval for the Early data.

22. Assume the Early and Late data in problem 21 represent the number of cler-

ical tasks correctly performed by college students, who are asked to perform

the tasks Early in the morning and then Late in the morning. Thus, student 4

performs 5 clerical tasks correctly Early in the morning and 7 correctly Late in

the morning.

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