Need help with chapter review questions attached.

1. For a fixed confidence level, in stating a confidence-interval

estimate of a population mean, the level of confidence increases as the

size of the interval _____________ .a.increases b. decreases c. remains

unchanged d. not enough information to determine

2. Which of the following statements regarding t-curves is/are true?

A. The total area under a t-curve with 10 degrees of freedom is greater

than the area under the standard normal curve.

B. The t-curve with 10 degrees of freedom is flatter and wider than the

standard normal curve.

C. The t-curve with 10 degrees of freedom more closely resembles the

standard normal curve than the t-curve with 20 degrees of freedom.

A

A & B

A & C

B

B & C

C

A, B, C

3.

Suppose that you wish to obtain a confidence interval for a population

mean. Under the conditions described below, should you use the

z-interval procedure, the t-interval procedure, or neither?

- The population standard deviation is known.- The population is not

normally distributed.- The sample size is 12.A. z-interval B. t-interval

C. neither

4. A researcher wishes to estimate the mean resting heart rate for

long-distance runners. A random sample of 12 runners yields the

following heart rates, in beats per minute.

80 81 61 79 59 6680 62 72 78 60 63

Use the data to obtain a point estimate of the mean resting heart rate

for all long distance runners.

A.66.7 beats per minute B. 68.4 beats per minute C. 70.1 beats per

minute D. 71.9 beats per minute

5. A college statistics professor has office hours from 9:00 am to 10:30

am daily. A sample of waiting times to see the professor (in minutes) is

10, 12, 20, 15, 17, 10, 30, 28, 35, 28, 19, 27, 25, 22, 33, 37, 14, 21,

20, 23. Assuming

o=

7.84 find the 95.44% confidence interval for the population mean.a. -3.5

to 3.5 minutes b. -7.7 to 7.8 minutes c. 18.8 to 25.8 minutes d. 19.5 to

35.1 minutes

6. Find the value of a which corresponds to a level of confidence of

93%.

a. 0.007 b. 0.07 c. 0.7 d. 0.93

7. The principal randomly selected six students to take an aptitude

test. Their scores were:79.3 81.3 71.4 89.6 89.2 76.3 Determine a 90%

confidence interval for the mean score for all students.

a. 75.17 to 87.20 b. 75.27 to 87.10 c. 87.10 to 75.27 d. 87.20 to 75.17

8. Suppose you have obtained a 95% confidence interval for . Which of

the following statements is/are true regarding the relationship between

precision and confidence level? Assume that the sample size is fixed.

A. Increasing the confidence level to 99% will result in a narrower

interval.

B. Decreasing the confidence level to 90% will result in greater

precision.

C. Decreasing the precision will result in a higher confidence level.

D. Increasing the precision will result in a higher confidence level.

A and C A and D B and C B and D

9. A sample of 45 eggs yields a mean weight of 1.37 ounces. Assuming

that o = 0.53 ounces, find the margin of error in estimating at the 95%

level of confidence.

a. 0.02 oz b. 0.13 oz c. 0.15 oz d. 6.71 oz

10. A population is normal with a variance of 51. Suppose you wish to

estimate the population mean Find the sample size needed to assure with

68.26 percent confidence that the sample mean will not differ from the

population mean by more than 4 units.

Hint: The VARIANCE is 51, so what is the standard deviation

a. 4 b. 11 c. 41 d. 163

11. For a t-curve with df = 11, find t0.10

a.1.280 b.1.363 c.1.372 d.2.718

12. d

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