MGMT 650 Quiz 7 Answers (2020) UMUC.docx

MGMT 650 Quiz 7 Answers (2020)
UMUC
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MGMT 650 Quiz 7 Answers (2020) UMUC
1. The report of a sample survey of 1014 adults says, "with 95% confidence, between 9% and 15% of all
Americans expect to spend more on gifts this year than last year." What does the phrase "95%
confidence" mean?
2. What is the critical value of t for a 90% confidence interval with df = 14? (Assume a 2-tailed test)
3. What is the critical value for a 95% confidence interval based on a sample size of 20? (Population
standard deviation is unknown). (Assume a 2-tailed test)
4. A survey of 30 random shoppers found a 95% confidence interval that shoppers will spend between
$24.50 and $28.30.
A second survey surveyed 25 random shoppers.
5. A survey of 521 citizens found that 342 of them favor a new bill introduced by the city.
We want to find a 95% confidence interval for the true proportion of the population who favor the bill.
What is the lower limit of the interval? (Round to 3 decimal digits)
6. Compute a 95% confidence interval for the population mean, based on the sample numbers 21, 28, 33,
34, 25, 26, and 135.
Which table do we use to find the margin of error?
7. Compute a 95% confidence interval for the population mean, based on the sample numbers 21, 28, 33,
34, 25, 26, and 135.
What is the Critical value? (Get 4 decimal digits).
8. Compute a 95% confidence interval for the population mean, based on the sample numbers 21, 28, 33,
34, 25, 26, and 135.
What is the margin of error? (Round to two decimal digits)
9. Compute a 95% confidence interval for the population mean, based on the sample numbers 21, 28, 33,
34, 25, 26, and 135.
Find the lower and upper limits of the interval.
10. Change the last value to 27 and re-compute the confidence interval.
The numbers now are: 21, 28, 33, 34, 25, 26, and 27
11. What is an outlier and how does it affect the confidence interval?
12. The director of admissions at the University of Maryland, University College is concerned about the high
cost of textbooks for the students each semester. A sample of 25 students enrolled in the university
indicates that x(bar) = $315.40 and s = $43.20.
13. The director of admissions at the University of Maryland, University College is concerned about the high
cost of textbooks for the students each semester. A sample of 25 students enrolled in the university
indicates that x(bar) = $315.40 and s = $43.20.
14. The director of admissions at the University of Maryland, University College is concerned about the high
cost of textbooks for the students each semester. A sample of 25 students enrolled in the university
indicates that x(bar) = $315.40 and s = $75. (Note the sample standard deviation is different from the first
part).

15. Explain the difference between parts A and C. In both parts we are asked whether or not there is
evidence that the population mean was over $300.
In part A: x(bar) = $315.40; s = $43.2; Sample size = 25
In part C: x(bar) = $315.40; s = $75; Sample size = 25