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Found in Mathematics: Statistics
Chapter 1, # 0
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Week 7 Questions

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1. (TCO 6) In the standard normal distribution, the variance is always (Points : 3)

1

2

none of these

2. (TCO 6) The area under a normal curve with mu = 15 and sigma = 2 is (Points : 3)

1

2

none of these

3. (TCO 6) If John gets an 80 on a physics test where the mean is 85 and the standard deviation is 3, where does he stand in relation to his classmates? (Points : 3)

He is in the top 5%.

He is in the top 10%.

He is in the bottom 5%.

He is the bottom 1%.

4. (TCO 6) In a normal distribution with mu = 25 and sigma = 9, what number corresponds to z = -2? (Points : 3)

21

16

7

none of these

5. (TCO 6) Let’s assume you have taken 100 samples of size 36 each from a normally distributed population. Calculate the standard deviation of the sample means if the population’s variance is 25. (Points : 3)

0.833

0.167

0.694

0.482

6. (TCO 6) The area to the left of ‘z’ is 0.0681. What z-score corresponds to this area? (Points : 3)

-1.40

1.49

-1.49

none of these

7. (TCO 6) Find P(9 < x < 22) when mu = 20 and sigma = 5. (Points : 3)

0.6554

0.6415

0.0139

0.3585

8. (TCO 7) What is the critical z-value that corresponds to a confidence level of 92%? (Points : 3)

approximately 1.48

approximately 1.55

approximately 1.75

none of these

(TCO 7) Compute the population mean margin of error for a 95% confidence interval when sigma is 4 and the sample size is 36. (Points : 3)

+/- 1.3066…

+/- 1.0966...

+/- 1.7166...

none of these

10. (TCO 7) A standard IQ test has a mean of 98 and a standard deviation of 16. We want to be 99% certain that we are within 8 IQ points of the true mean. Determine the sample size. (Points : 3)

16

27

26

none of these

11. (TCO 7) A private medical clinic wants to estimate the true mean annual income of its patients. The clinic needs to be within \$100 of the true mean. The clinic estimates that the true population standard deviation is around \$2,100. If the confidence level is 95%, find the required sample size in order to meet the desired accuracy. (Points : 6)

1,695

2,100

1,432

1,700

12. (TCO 7) An auditor wants to estimate what proportion of a bank’s commercial loan files are incomplete. The auditor wants to be within 7% of the true proportion when using a 95% confidence level. How many files must the auditor sample? No estimate of the proportion is available, so use 0.5 for the population proportion. (Points : 6)

196

150

200

180

1. (TCO 7) Interpret a 99% confidence interval of (5.355, 5.445) for a population mean. (Points : 6)

2. (TCO 7) A nursing school wants to estimate the true mean annual income of its alumni. It randomly samples 200 of its alumni. The mean annual income was \$55,200 with a standard deviation of \$1,500. Find a 95% confidence interval for the true mean annual income of the nursing school alumni. Write a statement about the confidence level and the interval you find. (Points : 6)

3. (TCO 7) An auditor wants to estimate what proportion of a bank’s commercial loan files are incomplete. The auditor randomly samples 60 files and finds 12 are incomplete. Using a 95% confidence interval, estimate the true proportion of incomplete files for ALL the bank’s commercial loans. Write a statement about the confidence level and the interval you find. (Points : 6)

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