Quiz: Standard Deviation and Confidence Interval Estimate
Chapter 9 Quiz
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1 Compute the critical value za/2 that corresponds to a 94% level of confidence.
A. 1.88
B. 1.66
C. 1.96
D. 2.33
2. In a sample of 10 randomly selected women, it was found that their mean height was 63.4 inches. Form previous studies, it is assumed that the standard deviation, σ, is 2.4. Construct the 95% confidence interval for the population mean.
A. (61.9, 64.9)
B. (58.1, 67.3)
C. (59.7, 66.5)
D. (60.8, 65.4)
3. Suppose a 95% confidence interval for µ turns out to be (120, 310). To make more useful inferences from the data, it is desired to reduce the width of the confidence interval. Which of the following will result in a reduced interval width?
A. Increase the sample size.
B. Decrease the confidence level.
C. Increase the sample size and decrease the confidence level.
D. All of the choices will result in a reduced interval width.
4. A nurse at a local hospital is interested in estimating the birth weight of infants. How large a sample must she select if she desires to be 90% confidence that the true mean is within 4 ounces of the sample mean? The standard deviation of the birth weights is known to be 6 ounces.
A. 10
B. 9
C. 8
D. 7
5. Let t0 be a specific value of t. Find t0 such that the following statement is true:
P(t < t0) = 0.05 where df = 20)
A. -1.729
B. 1.729
C. -1.725
D. 1.725
6. When 335 college students were surveyed, 130 said they own their car. Find a point estimate for p, the population proportion of students who own their cars.
A. 0.285
B. 0.388
C. 0.612
D. 0.634
7. Many people think that a national lobby’s successful fight against gun control legislation is reflecting the will of a minority of Americans. A random sample of 4000 citizens yielded 2250 who are in favor if gun
1 |2 |3 |4 |5 |6 |7 |8 |9 |10 |11 |12 |13 |14 |15 | | | | | | | | | | | | | | | | | |
1 Compute the critical value za/2 that corresponds to a 94% level of confidence.
A. 1.88
B. 1.66
C. 1.96
D. 2.33
2. In a sample of 10 randomly selected women, it was found that their mean height was 63.4 inches. Form previous studies, it is assumed that the standard deviation, σ, is 2.4. Construct the 95% confidence interval for the population mean.
A. (61.9, 64.9)
B. (58.1, 67.3)
C. (59.7, 66.5)
D. (60.8, 65.4)
3. Suppose a 95% confidence interval for µ turns out to be (120, 310). To make more useful inferences from the data, it is desired to reduce the width of the confidence interval. Which of the following will result in a reduced interval width?
A. Increase the sample size.
B. Decrease the confidence level.
C. Increase the sample size and decrease the confidence level.
D. All of the choices will result in a reduced interval width.
4. A nurse at a local hospital is interested in estimating the birth weight of infants. How large a sample must she select if she desires to be 90% confidence that the true mean is within 4 ounces of the sample mean? The standard deviation of the birth weights is known to be 6 ounces.
A. 10
B. 9
C. 8
D. 7
5. Let t0 be a specific value of t. Find t0 such that the following statement is true:
P(t < t0) = 0.05 where df = 20)
A. -1.729
B. 1.729
C. -1.725
D. 1.725
6. When 335 college students were surveyed, 130 said they own their car. Find a point estimate for p, the population proportion of students who own their cars.
A. 0.285
B. 0.388
C. 0.612
D. 0.634
7. Many people think that a national lobby’s successful fight against gun control legislation is reflecting the will of a minority of Americans. A random sample of 4000 citizens yielded 2250 who are in favor if gun