2 bng Chapter 8 10. A random sample of 85 group leaders, supervisors, and simila

Question

2 bng Chapter 8 10. A random sample of 85 group leaders, supervisors, and similar personnel revealed that on the average a person spent 6.5 years on the job before being promoted. The standard deviation of the sample was 1.7 years. Using the 0.95 degree of confidence, what is the confidence interval within which the population mean lies? a. 6.99 and 7.99 b. 4.15 and 7.15 c. 6.14 and 6.86 d. 6.49 and 7.49 e. None of the above 11. In a manufacturing process, a random sample of 9 bolts has a mean length of 3 inches with a variance of .09. What is the 90 percent confidence interval for the true mean length of the a. 2.8355 to 3.1645 b. 2.5065 to 3.4935 c. 2.4420 to 3.5580 d. 2.8140 to 3.1860 e. 2.9442 to 3.0558 Suppose that, for a sample size n 100 measurements, we find that 50. Assuming that o 2, calculate confidence intervals for the population mean H with the following confidence levels 12. Confidence Interval of 99.73% a. 49.485 to 50.515 lb. 56.3 to 60.4 c. 54.3 to 58.4 d. 48.23 to 50.5 e. 49.4 to 50.6 13. In a manufacturing process, a random sample of36 bolts has a mean length of 3 inches with a standard deviation (s) of.3 inches. What is the 99 percent confidence interval for the true mean length of the bolt? a. 2.902 to 3.098 b. 2.884 to 3.117 c. 2.864 to 3.136 d. 2.228 to 3.772 e. 2.802 to 3.198

Explanation / Answer

Answer:

10. c. 6.14 and 6.86

Confidence interval - mean

95%

confidence level

6.5

mean

1.7

std. dev.

85

n

1.960

z

0.361

half-width

6.861

upper confidence limit

6.139

lower confidence limit

11). D. 2.8140 to 3.1860

Confidence interval - mean

0.9000

confidence level

3.0000

mean

0.3000

std. dev.

9.0000

n

1.8595

t (df = 8)

0.1860

half-width

3.1860

upper confidence limit

2.8140

lower confidence limit

12). e. 49.4 to 50.6

Confidence interval - mean

99.73%

confidence level

50.0000

mean

2.0000

std. dev.

100.0000

n

3.000

z

0.600

half-width

50.600

upper confidence limit

49.400

lower confidence limit

13). c. 2.864 to 3.136

Confidence interval - mean

99%

confidence level

3.0000

mean

0.3000

std. dev.

36.0000

n

2.724

t (df = 35)

0.136

half-width

3.136

upper confidence limit

2.864

lower confidence limit

14).67.833 to 76.167

Confidence interval - mean

98%

confidence level

72.0000

mean

5.0000

std. dev.

11.0000

n

2.764

t (df = 10)

4.167

half-width

76.167

upper confidence limit

67.833

lower confidence limit

15). C. 2.012

16). A. 0.1608 to 0.2392

Confidence interval - proportion

95%

confidence level

0.2000

proportion

400.0000

n

1.960

z

0.039

half-width

0.2392

upper confidence limit

0.1608

lower confidence limit

17). Answer: a.

Confidence interval - proportion

95%

confidence level

0.6000

proportion

50.0000

n

1.960

z

0.136

half-width

0.736

upper confidence limit

0.464

lower confidence limit

Confidence interval - proportion

98%

confidence level

0.6000

proportion

50.0000

n

2.326

z

0.161

half-width

0.761

upper confidence limit

0.439

lower confidence limit

Confidence interval - proportion

99%

confidence level

0.6000

proportion

50.0000

n

2.576

z

0.178

half-width

0.778

upper confidence limit

0.422

lower confidence limit

Confidence interval - mean

95%

confidence level

6.5

mean

1.7

std. dev.

85

n

1.960

z

0.361

half-width

6.861

upper confidence limit

6.139

lower confidence limit

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