Posted: September 16th, 2017

DeVry Chicago MATH 221 WEEK 7 QUIZ

1. Question : (TCO 6) In the standard normal distribution, the variance is always
Student Answer: 0 1 2 none of these
2. Question : (TCO 6) The area under a normal curve with mu = 15 and sigma = 2 is
Student Answer: 0 1 2 none of these
3. Question : (TCO 6) If Mary gets a 90 on a physics test where the mean is 85 and the standard deviation is 4.59, where does she stand in relation to her classmates?
Student Answer: She is in the top 15%. She is in the bottom 15%. She is in the top 5%. She is in the bottom 5%.
4. Question : (TCO 6) In a normal distribution with mu = 25 and sigma = 6, what number corresponds to z = 3?
Student Answer: 40 43 46 none of these
5. Question : (TCO 6) Let’s assume you have taken 100 samples of size 49 each from a normally distributed population. Calculate the standard deviation of the sample means if the population’s variance is 16.
Student Answer: 0.571 0.429 0.327 0.107
6. Question : (TCO 6) The area to the left of ‘z’ is 0.0681. What z-score corresponds to this area?
Student Answer: -1.40 1.49 -1.49 none of these
7. Question : (TCO 6) Find P(11 < x < 16) when mu = 15 and sigma = 3.
Student Answer: 0.6293 0.3707 0.0918 0.5393
8. Question : (TCO 7) What is the critical z-value that corresponds to a confidence level of 92%?
Student Answer: approximately 1.48 approximately 1.55 approximately 1.75 none of these
9. Question : (TCO 7) Compute the population mean margin of error for a 99% confidence interval when sigma is 4 and the sample size is 36.
Student Answer: +/- 1.3066… +/- 1.0966… +/- 1.7166… none of these
10. Question : (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.
Student Answer: 16 27 26 none of these
11. Question : (TCO 7) A private medical clinic wants to estimate the true mean annual income of its patients. The clinic needs to be within $200 of the true mean. The clinic estimates that the true population standard deviation is around $1,300. If the confidence level is 95%, find the required sample size in order to meet the desired accuracy.
Student Answer: 205 163 200 150
12. Question : (TCO 7) An auditor wants to estimate what proportion of a bank’s commercial loan files are incomplete. The auditor wants to be within 4% 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.
Student Answer: 550 610 601 580
ESSAY QUESTIONS1. Question : (TCO 7) Interpret a 90% confidence interval of (4.355, 4.445) for a population mean.
2. Question : (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.
3. Question : (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.

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