STAT151 Study Guide - Midterm Guide: Simple Random Sample, Stratified Sampling, Confidence Interval
Statistics 151 Practice Midterm 2 – Mike Kowalski
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Statistics 151 Practice Midterm 2 – Multiple Choice (50 minutes)
Instructions:
1. This is a closed book exam.
2. You may use the STAT 151 formula sheets and tables provided and a NON-PROGRAMMABLE calculator only.
3. You have 50 minutes to complete the exam.
4. The exam consists of 25 multiple choice questions worth 1 mark each.
5. Topics covered: Chapters 1 – 8 in Agresti/Franklin 2.
1. The number of undergraduates at Johns Hopkins University is approximately 2000, while the number at Ohio State
University is approximately 40,000. At both schools a simple random sample of about 3% of the undergraduates is taken.
We conclude that
A) the sample from Johns Hopkins has almost the same sampling variability as that from Ohio State.
B) it is impossible to make any statements about the sampling variability of the two samples because the students
surveyed were different.
C) the sample from Johns Hopkins has more sampling variability than that from Ohio State.
D) the sample from Johns Hopkins has less sampling variability than that from Ohio State.
Use the following to answer questions 2-3:
An agricultural researcher plants twenty-five plots with a new variety of corn. The average yield for these plots is 150 bushels
per acre with standard deviation of 10. Assume that the yield per acre for the new variety of corn follows a normal distribution.
2. A 95% confidence interval for µ is
A) 150 ± 3.42. B) 150 ± 3.92. C) 150 ± 4.13. D) 150 ± 4.98.
3. Which of the following would produce a confidence interval with a smaller margin of error than the 95% confidence
interval you computed above?
A) Plant 100 plots rather than 25.
B) Compute a 99% confidence interval rather than a 95% confidence interval. The increase in confidence indicates
that we have a better interval.
C) Plant only 5 plots rather than 25, since 5 are easier to manage and control.
D) None of the above.
4. A statistic is said to be unbiased if
A) it is used for only honest purposes.
B) the mean of its sampling distribution is equal to the true value of the parameter being estimated.
C) the survey used to obtain the statistic was designed so as to avoid even the hint of racial or sexual prejudice.
D) both the person who calculated the statistic and the subjects whose responses make up the statistic were truthful.
5. Ignoring twins and other multiple births, assume babies born at a hospital are independent events with the probability
that a baby is a boy and the probability that a baby is a girl both equal to 0.5. If the first 4 children born are girls, what
is the probability the next born child is a boy?
A) 0.5. B) 1.0. C) 0.75. D) 0.8.
6. A television station is interested in predicting whether or not voters are in favor of an increase in the state sales tax. It
asks its viewers to phone in and indicate whether they support or are opposed to an increase in the state sales tax in
order to generate additional revenue for education. Of the 2633 viewers who phone in, 1474 (55.98%) are opposed to
the increase. The sample obtained is
A) probably biased.
B) a simple random sample.
C) a stratified random sample.
D) a probability sample in which each person in the population has the same chance of being in the sample.
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STAT151 Full Course Notes
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Document Summary
If the first 4 children born are girls, what is the probability the next born child is a boy: 0. 5. D) 0. 8: a television station is interested in predicting whether or not voters are in favor of an increase in the state sales tax. It asks its viewers to phone in and indicate whether they support or are opposed to an increase in the state sales tax in order to generate additional revenue for education. Of the 2633 viewers who phone in, 1474 (55. 98%) are opposed to the increase. The sample obtained is: probably biased, a simple random sample, a stratified random sample, a probability sample in which each person in the population has the same chance of being in the sample. Statistics 151 practice midterm 2 multiple choice (50 minutes) You may use the stat 151 formula sheets and tables provided and a non-programmable calculator only. You have 50 minutes to complete the exam.
