USE THIS INFORMATION BELOW FOR THE NEXT 3 QUESTIONS (1-3)
In order to estimate the average time spent on the computer terminals per student at a local university, data were collected from a sample of 144 business students over a one-week period. Assume the population standard deviation is 1.2 hours.
1. The standard error of the mean is approximately
2. With a 0.95 probability, the margin of error is approximately
3. If the sample mean is 9 hours, then the 95% confidence interval is approx.
a. 7.04 to 110.96 hours
b. 8.80 to 9.20 hours
c. 7.80 to 10.20 hours
d. 8.74 to 9.26 hours
11. It is desired to estimate the average total compensation of CEOs in the Service industry. Data were randomly collected from 18 CEOs and the 97% confidence interval was calculated to be ($2,181,260, $5,836,180). Which of the following interpretations is correct?
a) 97% of the sampled total compensation values fell between $2,181,260 and $5,836,180.
b) We are 97% confident that the mean of the sampled CEOs falls in the interval $2,181,260 to $5,836,180.
c) In the population of Service industry CEOs, 97% of them will have total compensations that fall in the interval $2,181,260 to $5,836,180.
d) We are 97% confident that the average total compensation of all CEOs in the Service industry falls in the interval $2,181,260 to $5,836,180.
Use the information in the table below for questions 12 – 16
The following are the durations in minutes of a sample of long-distance phone calls made within the continental United States reported by one long-distance carrier.
Time (in Minutes) Frequency
0 but less than 5 0.37
5 but less than 10 0.22
10 but less than 15 0.15
15 but less than 20 0.10
20 but less than 25 0.07
25 but less than 30 0.07
30 or more 0.02
12. If 1,000 calls were randomly sampled, how many calls lasted 10 minutes or more?
13. If 100 calls were randomly sampled, how many calls lasted less than 15 minutes?
14. If 10 calls lasted 30 minutes or more, how many total calls were in the sample?
15. What is the cumulative relative frequency for the % of calls that lasted < 10 minutes? a) 0.10 b) 0.59 c) 0.76 d) 0.84 16. If 100 calls were sampled, _______ of them would have lasted 15 or more minutes. a) 26 b) 74 c) 10 d) None of the above. 17. Since the population size is always larger than the sample size, then the sample statistic a. can never be larger than the population parameter b. can never be equal to the population parameter c. can never be zero d. can never be smaller than the population parameter e. None of the above answers is correct. 18. The measure of location that is the most likely to be influenced by extreme values in the data set is the a. range b. median c. mode d. mean e. None of the above answers is correct. 19. For a normal distribution, a negative value of z indicates a. a mistake has been made in computations, because z is always positive b. the area corresponding to the z is negative c. the z is to the left of the mean d. the z is to the right of the mean e None of the above answers is correct. 20. A confidence interval was used to estimate the proportion of statistics students that are females. A random sample of 72 statistics students generated the following 90% confidence interval: (0.438, 0.642). Based on the interval above, is the population proportion of females equal to 0.60? a) No, and we are 90% sure of it. b) No. The proportion is 54.17%. c) Maybe. 0.60 is a believable value of the population proportion based on the information above. d) Yes, and we are 90% sure of it.
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