Exam 7: Confidence Intervals and Sample Size
Exam 1: The Nature of Probability and Statistics81 Questions
Exam 2: Frequency Distributions and Graphs107 Questions
Exam 3: Data Description127 Questions
Exam 4: Probability and Counting Rules173 Questions
Exam 5: Discrete Probability Distributions117 Questions
Exam 6: The Normal Distribution114 Questions
Exam 7: Confidence Intervals and Sample Size122 Questions
Exam 8: Hypothesis Testing178 Questions
Exam 9: Testing the Difference Between Two Means, Two Variances, and Two Proportions99 Questions
Exam 10: Correlation and Regression73 Questions
Exam 11: Other Chi-Square Tests73 Questions
Exam 12: Analysis of Variance69 Questions
Exam 13: Nonparametric Statistics62 Questions
Exam 14: Sampling and Simulation58 Questions
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A chi-square variable cannot be negative, and the distributions are positively skewed.
(True/False)
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The prices (in dollars) for a graphing calculator are shown below for 8 online vendors. Estimate the true mean price for this particular calculator with 95% confidence.
121 125 151 129
127 133 121 125
(Multiple Choice)
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Jennifer wants to find a 95% confidence interval for the time it takes her to get to work.
She kept records for 30 days and found her average time to commute to work was 20.5
minutes with a standard deviation for the population of 3.9 minutes. Jennifer's margin of
error would be 1.4 minutes.
(True/False)
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In order to find confidence intervals for variances and standard deviations, one
must assume that the variable is .
(Short Answer)
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A random sample of 50 voters found that 46% were going to vote for a certain candidate. Find the 95% limit for the population proportion of voters who will vote for that
Candidate.
(Multiple Choice)
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The confidence level of an interval estimate of a parameter is the probability that the
interval estimate will contain the parameter.
(True/False)
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The Pizza Shop wanted to determine what proportion of its customers ordered only cheese pizza. Out of 80 customers surveyed, 15 ordered only cheese pizza. What is the
99% confidence interval of the true proportion of customers who order only cheese
Pizza?
(Multiple Choice)
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Measurements were made of the milk fat content (in percent) in six brands of feta cheese variety of goat cheese), with the following results. Assume that the population is normally distributed.
27.5 19.3 32.0 23.5 24.6 16.9
Construct a confidence interval for the population standard deviation .
(Multiple Choice)
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A population has a standard deviation . How large a sample must be drawn so that a confidence interval for will have a margin of error equal to
(Multiple Choice)
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Find the 95% confidence interval for the standard deviation of the lengths of pipes if a sample of 11 pipes has a standard deviation of 10.6 inches.
(Multiple Choice)
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The rounding rule for a confidence interval for a proportion is to round off to three
decimal places.
(True/False)
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Find the critical value needed to construct a confidence interval of the given level with the given sample size.
Level , sample size 11
(Multiple Choice)
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A study of elephants is conducted to determine the average weight of a certain subspecies of elephants. The standard deviation for the population is 500 pounds. At a
90% level, how many elephants need to be weighed so the average weight will be
Accurate to within 250 pounds?
(Multiple Choice)
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Find the level of the confidence interval that has the given critical value. 2.16
(Multiple Choice)
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Find the margin of error for the given confidence level and values of and . , confidence level
(Multiple Choice)
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In a sample of 45 mice, a biologist found that 40% were able to run a maze in 30 seconds or less. Find the 95% limit for the population proportion of mice who can run a maze in
30 seconds or less.
(Multiple Choice)
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