Practice Exam 2 – STCC204 The following are the types ... - Statistics

Practice Exam 2 – STCC204
The following are the types of questions you can expect on Exam 2. There are 24 questions on this
practice exam, so it should give you a good indication of the length of the exam. On Exam 2 the 25 th
question will be “Turn in your crib sheet with your exam paper”. With only 24 questions, it is not
possible to address all of the topics we covered. You need to study your other assignments and lecture
notes to be sure you have studied adequately.
1. Which of the following statements regarding the normal distribution is NOT true?
A) The mean, median and mode are all equal.
B) It has a single peak.
C) It is symmetrical.
D) The points of the curve meet the X-axis at z = -3 and z = 3.
E) All of the above are true.
2. The mean of a normally distributed group of weekly incomes of a large group of executives is $1,000
and the standard deviation is $100. What is the z-score for an income of $1,100?
A) 1.00
B) 2.00
C) 1.683
D) -0.90
E) None of the above
3. Ball-Bearings, Inc. produces ball bearings automatically on a Kronar BBX machine. For one of the
ball bearings, the mean diameter is set at 20.00 mm (millimeters). The standard deviation of the
production over a long period of time was computed to be 0.150 mm. What percentage of the ball
bearings will have diameters 20.27 mm or less? (Assume a normal population).
A) 41.00%
B) 12.62%
C) 96.41%
D) 85.00%
E) 3.59%
4. The average score of 100 students taking a statistics final was 70 with a standard deviation of 7.
Assuming a normal distribution, what proportion of the students scored 90 or higher?
A) 0.4979
B) 0.0021
C) 0.9979
D) 2.86
E) None of the above
5. What is the area under the normal curve between z = -1.0 and z = -2.0?
A) 0.0228
B) 0.3413
C) 0.1359
D) 0.4772
E) None of the above
ST204 Practice Exam 2 – Page 1 of 4

6. Past experience of a large manufacturing firm with administering a test to recent college graduates
who had applied for a job revealed that the mean test score was 500, and the standard deviation was 50.
The distribution of the test scores was normal. Based on this experience, management is considering
placing a person whose score is in the upper 6 percent of the distribution directly into a responsible
position. What is the lowest score a college graduate must earn to qualify for a responsible position?
A) 50
B) 625
C) 460
D) 578
E) None of the above
7. A graphical procedure that can be used to help decide whether or not a simple random sample was
obtained from a normal population is a normal __________ plot.
A) proportion
D) frequency
B) scatter
E) probability
C) linear
8. Which of the following is NOT a valid reason for selecting a sample instead of studying the whole
population?
A) The cost of studying an entire population may be too high.
B) The population may be at least partially destroyed in the process of studying it.
C) Studying the entire population might be too time consuming.
D) All of the above are valid reasons for sampling.
9. Suppose we sample by selecting every fifth invoice in a file after randomly obtaining a starting point.
What type of sampling is this?
A) simple random sampling
D) systematic random sampling
B) cluster random sampling
E) None of the above
C) stratified random sampling
10. The _______ sampling method typically will require a larger sample size than other methods;
however, the close proximity of sample elements can be cost-effective.
A) simple random
D) systematic
B) cluster
E) None of the above.
C) stratified
11. All possible samples of size n are selected from a population, and the mean of each sample is
determined. The mean of the sample means is _________.
A) Exactly the same as the population mean D) Cannot be estimated in advance
B) Larger than the population mean
E) None of the above
C) Smaller than the population mean
12. A population consists of 15 items. If a sample of size 8 is to be drawn from this population, how
many possible samples could be obtained?
A) 120
B) 6,435
C) 9,911,479
D) 259,459,200
E) None of the above
ST204 Practice Exam 2 – Page 2 of 4

13. When obtaining a sample (with n > 1) from a population of size N, the amount of dispersion in the
sampling distribution of the sample mean will always be
A) greater than the dispersion in the population.
B) less than the dispersion in the population.
C) about the same as the dispersion in the population.
D) Cannot determine from the information given.
14. The ___________ tells us that the distribution of all possible sample means will be approximately
normal for reasonably large sample sizes.
A) Central Limit Theorem
D) Estimation Theorem
B) Mean Limit Theorem
E) None of the above is correct.
C) Combination Theorem
15. The quality management division of a company that manufactures tires requires the average diameter
of a certain model tire to be 36 inches, and the standard deviation of the diameters to be .2 inches.
Assuming the parameters are as stated, if a sample of size 43 is to be taken from this population of tires,
what is the value of the standard error of the mean?
A) .2000
B) .0056
C) .0047
D) .0333
E) .0305
σ X
16. The value measures
A) the amount of dispersion in the sample.
B) the amount of dispersion in all of the samples.
C) the amount of dispersion in the set of all possible sample means.
D) the amount of dispersion in the population from which a sample is obtained.
E) None of the above.
17. Cereal boxes are filled using a machine that dispenses an average of 15 ounces per box with a
standard deviation of 0.75 ounces. A sample of 100 boxes will be obtained. Determine the range of
values that will contain approximately 97% of the possible sample means.
A) 13.37 to 16.63
B) 12.83 to 17.17
C) 14.25 to 15.75
D) 14.84 to 15.16
E) None of the above
18. The finite population correction factor is usually ignored if the sample size is less than what
percentage of the population?
A) 5%
D) 100%
B) 10%
E) None of the above
C) 50%
ST204 Practice Exam 2 – Page 3 of 4

19. Suppose 1,600 of 2,000 registered voters sampled said they planned to vote for the Republican
candidate for president. Using 95% confidence, what is the interval estimate for the population
proportion?
A) .782 to .818
B) .692 to .864
C) .765 to .835
D) .777 to .823
E) None of the above
20. A 95 percent confidence interval implies that about 95 out of 100 similarly constructed intervals will
include the _____________ being estimated.
A) sample
D) population
B) statistic
E) None of the above
C) parameter
21. Other things being equal, a smaller sample size would result in
A) a wider confidence interval.
D) greater confidence in our estimation procedure
B) a narrower confidence interval
E) None of the above
C) a more reliable confidence interval
22. A health care worker was investigating the cost of hospital care. A sample of 44 hospitals showed an
average daily cost of $352.00, and a standard deviation of $41.00. Give a 98% confidence interval for the
average daily cost for all hospitals in the population.
A) $337.60 to $366.40
B) $342.73 to $361.27
C) $333.61 to $370.39
D) $349.75 to $354.26
E) $345.82 to $358.18
23. A member of Congress wants to determine her popularity in a certain part of the state. She indicates
that the proportion of voters who will vote for her must be estimated within plus or minus 2 percent of the
population proportion. Further, a 95% confidence level will be used. In past elections, the representative
received 40 percent of the popular vote in that area of the state. She doubts whether it has changed much.
How many registered voters should be sampled?
A) 864
B) 5200
C) 2305
D) 2000
E) None of the above
24. The mean number of travel days per year for the outside salespeople employed by hardware
distributors is to be estimated. A 90% confidence level will be used. The mean of a small pilot study was
150 days, with a standard deviation of 14 days. If the population mean is to be estimated within two days,
how many outside salespeople should be sampled?
A) 134
B) 452
C) 511
D) 2100
E) None of the above
ANSWERS: 1.D; 2.A; 3.C; 4.B; 5.C; 6.D; 7.E; 8.D; 9.D; 10.B; 11.A; 12.B; 13.B; 14.A; 15.E; 16.C;
17.D; 18.A; 19.A; 20.C; 21.A; 22.A; 23.C; 24.A
ST204 Practice Exam 2 – Page 4 of 4