The trade volume of a stock is the number of shares traded on a given day. The followingdata, in millions(so that 2.45 represents2,450,000 sharestraded), represent the volume of a certain stock traded for a random sample of 40 trading days in 2007. Complete parts(a) through(d).

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(a) Use the data to compute a point estimate for the population mean number of shares traded per day in 2007.

The point estimate of the population mean number of shares is

nothing

million.

(Round to three decimal places asneeded.)

(b) Construct a90% confidence interval for the population mean number of shares traded per day in 2007.

The lower bound is

nothing

million.

(Round to three decimal places asneeded.)

The upper bound is

nothing

million.

(Round to three decimal places asneeded.)

Interpret the confidence interval. Choose the correct answer below.

A.

There is90% confidence that the mean number of shares of the stock traded per day in 2007 was greater than the upper bound of the confidence interval.

B.

There is90% confidence that the mean number of shares of the stock traded per day in 2007 was less than the lower bound of the confidence interval.

C.

There is90% confidence that the mean number of shares of the stock traded per day in 2007 was between the lower and upper bounds of the confidence interval.

(c) A second random sample of 40 days in 2007 resulted in the following data. Construct another90% confidence interval for the population mean number of shares traded per day in 2007.

4.23

5.46

2.37

7.49

4.96

2.41

6.35

4.65

5.19

2.38

3.32

2.44

2.34

2.74

1.37

1.6

1.71

1.64

2.2

1.43

1.48

2.05

3.75

3.3

2.7

2.44

1.67

1.38

3.12

1.69

1.79

2.05

3.59

1.79

2.2

1.54

0.84

2.19

1.69

1.77

The lower bound is

nothing

million.

(Round to three decimal places asneeded.)

The upper bound is

nothing

million.

(Round to three decimal places asneeded.)

Interpret the confidence interval. Choose the correct answer below.

A.

There is90% confidence that the mean number of shares of the stock traded per day in 2007 was between the lower and upper bounds of the new confidence interval.

B.

There is90% confidence that the mean number of shares of the stock traded per day in 2007 was less than the lower bound of the new confidence interval.

C.

There is90% confidence that the mean number of shares of the stock traded per day in 2007 was greater than the upper bound of the new confidence interval.

(d) Explain why the confidence intervals obtained in parts(b) and(c) are different. Choose the correct answer below.

A.

The confidence intervals are different because the values of t2 are different for different samples.

B.

The confidence intervals are different because of variation in sampling. The samples have the same standard deviations but different means that lead to different confidence intervals.

C.

The confidence intervals are different because of variation in sampling. The samples have different means and standard deviations that lead to different confidence intervals.

D.

The confidence intervals are different because of variation in sampling. The samples have the same means but different standard deviations that lead to different confidence intervals.