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1. An auditor for a large oil corporation has taken a random sample of monthly credit
card charges for 32 individual (non-corporate) accounts. She found a mean of $81.76.
Assume that the population standard deviation is 48.2. A 98% confidence interval
estimate for the population mean of individual credit card charges would be. (Points: 2)
A) 81.76 ± 19.89
B) 81.76 ± 16.72
C) 81.76 ± 112.94
D) 81.76 ± 22.0
2. Your statistics instructor wants you to determine a confidence interval estimate for the
mean test score for the next exam. In the past, the test scores have been normally
distributed with a mean of 74.2 and a standard deviation of 30.9. A 95% confidence
interval estimate if your class has 30 students is: (Points: 2)
A) 68.72 to 79.68
B) 13.64 to 134.76
C) 64.92 to 83.48
D) 63.14 to 85.26
3. You are interested in determining the average cost of a 3-minute telephone call to
locations within the continental U.S. What sample size must you take to be 96%
confident that the results will be within $.75 of the true mean cost per call? From the
phone company, you have gotten an estimate of = 7.71. (Points: 2)
A) 185
B) 445
C) 406
D) 574
4. The Arkansas State Police wish to estimate the average mph being traveled on the
Interstate Highways, which cross the state. If the estimate is to be within 8 mpg of the
true mean with 98% confidence and the estimated standard deviation is 22 mph, how
large a sample size must be taken? (Points: 2)
A) 42
B) 15
C) 329
D) 14
5. Which of the following is not a part of the formula for constructing a confidence
interval estimate of the population mean? (Points: 2)
A) A point estimate of the population mean
B) The standard error of the sampling distribution of the sample mean
C) The confidence level
D) The value of the population mean
6. A Type II error is the probability of rejecting a true null hypothesis. (Points: 2)
7. If we reject the null hypothesis, we conclude that: (Points: 2)
A) there is enough statistical evidence to infer that the alternative hypothesis is true
B) there is not enough statistical evidence to infer that the alternative hypothesis is
C) there is enough statistical evidence to infer that the null hypothesis is true
D) the test is statistically insignificant at whatever level of significance the test was
conducted at
8. Consider testing the hypothesis H0: = 800 vs. H1:
statistic z equals 1.75, then the p-value is: (Points: 2)
A) 0.0401
B) 0.0802
C) 0.4599
D) 0.9198
≠ 800 If the value of the test
9. A mortgage broker is offering home mortgages at a rate of 9.5% but is fearful that this
value is higher than many others are charging. A sample of 40 mortgages filed in the
county court house shows an average of 9.25% with a standard deviation of 8.61%. Does
this sample indicate a smaller average? Use σ = 0.05 and assume a normally distributed
population. (Points: 2)
A) Yes, the test statistic falls in the rejection region.
B) No, the test statistic falls in the acceptance region.
C) Yes, because the test statistic is greater than -1.645.
D) No, because the test statistic is -1.85 and falls in the rejection region.
10. In testing the hypotheses
= 0.40
> 0.40
at the 5% significance level, if the sample proportion is .45, and the standard error of the
sample proportion is .035, the appropriate conclusion would be:
(Points: 2)
A) to reject H0
B) not to reject H0
C) to reject H1
D) to reject both H0 and H1