7.) What is another name for the standard deviation of the variable x? What is the reason for thatname?

Choose the correct answer below.

A.Another name is standard error of the mean because the standard deviation of x determines the amount of sampling error to be expected when a population mean is estimated by a sample mean.

B.Another name is sampling error of the mean because the standard deviation of x determines the amount of variation to be expected when a population mean is estimated by a sample mean.

C. Another name is sample mean because the standard deviation of x determines the average amount of deviation to be expected when a population mean is estimated by a sample mean.

D.Another name is standard change of the mean because the standard deviation of x determines the amount of variation to be expected when a population mean is estimated by a sample mean.

10 For earthquakes with a magnitude 7.5 or greater on the Richterscale, the time between successive earthquakes has a mean of 452 days and a standard deviation of 379 days. Suppose that you observe a sample of four times between successive earthquakes that have a magnitude of 7.5 or greater on the Richter scale.

a. Onaverage, what would you expect to be the mean of the fourtimes?

b. How much variation would you expect from your answer in part(a)? (Hint: Use thethree-standard-deviations rule.)

a. Onaverage, what would you expect to be the mean of the fourtimes? (?)

days

A census was taken of 50 regions to determine the percentage of adults in each region who have completed abachelor's degree. The accompanying table shows the results.

a. Obtain the standard deviation of the variable"percentage of adults who have completed abachelor's degree" for the population of 50 regions.

=

nothing

(Round to two decimal places asneeded.)

22

28

25

19

31

35

35

28

26

29

31

23

32

24

26

30

22

20

27

35

37

24

33

20

24

27

26

22

32

35

24

32

26

26

24

24

29

27

32

23

24

24

25

30

32

35

31

17

25

25

12 A statistic is said to be an unbiased estimator of a parameter if the mean of all its possible values equals theparameter; otherwise, it is said to be a biased estimator. An unbiased estimatoryields, onaverage, the correct value of theparameter, whereas a biased estimator does not.

a. Is the sample mean an unbiased estimator of the populationmean? Explain your answer.

b. Is the sample median an unbiased estimator of the populationmedian?

a. Choose the correct choice below.

A.The sample mean is a biased estimator of the populationmean, because the mean of the sampling distribution of x, x, is never equal to .

B.The sample mean is a biased estimator of the populationmean, because the mean of the sampling distribution of x, x, is only sometimes equal to . Consider taking samples of size 2 from the followingpopulation: 0,0, and 6. This results in =3 but x=2.

C.The sample mean is a biased estimator of the populationmean, because the mean of the sampling distribution of x, x, is only sometimes equal to . Consider taking samples of size 2 from the followingpopulation: 2,2, and 2. This results in =3 but x=2.

D.The sample mean is an unbiased estimator of the populationmean, because the mean of the sampling distribution of x, x, is always equal to .