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STAT 5325 – Exam 1 – Spring, 2009 – Blue Exam - Printed Name_______________________
Numbers in parenthesis is the question number on the white exam.
1. (30.)What will be the margin of error of a 80% confidence interval for a mean of a normal distribution given n =
225, and  = 30?
a. 3.92
b. 3.29
c. 2.56
d. none of the other answers are correct
2.(3.) Suppose that the status quo before an audit is that everything is okay with the recorded receipts. What is a
Type 2 error in this case?
a. Saying that some of the recorded receipts are in error when actually all are okay.
b. Saying that some of the recorded receipts are in error
c. Saying that the recorded receipts are okay when actually some are in error.
d. Saying that the recorded receipts are okay when actually all are okay
3.(20.) What t-table value would use if degrees of freedom are 14 and the confidence is 0.98?
a. 3.05
b. 1.97
c. 2.68
d. none of the other answers are correct
4. (16.)What is the formula for a margin of error of a sample mean if the population standard deviation is unknown.
s
a. t
b. t
c.
d.
n


n
n
s
n
5. (20.)If you take samples of size 6 from each of three populations, what is the rejection region for testing for
equality of the three population means? Reject Ho if
a. F > 3.68
b. 2 > 5.99
c. t > 1.96
d. z > 0.05
6. (9.) What would be the conclusion for a 90% confidence interval for a mean if x = $50 and the margin of error is
$3.05?
a. We are 90% confident that the sample mean falls outside the range $46.95 and $53.05
b. We are 90% confident that the population mean falls outside the range $46.95 and $53.05
c. We are 90% confident that the population mean falls between $46.95 and $53.05
d. Can not be determined unless degrees of freedom are known.
7. (22.) The width of bars in a histogram for the empirical rule
a. have no meaning since only the height of a histogram has any value.
b. correspond to the value of the population standard deviation
c. is arbitrarily chosen by the creator of the histogram
d. is the population mean
8. (12.)What is the importance of taking a random sample?
a. reduces bias
b. allows proportions to become the same as probabilities
c. is a requirement of all our tests and confidence intervals
d. All of the other answers are correct.
9. (17.)If  = 35, what sample size would you need to get the standard error to be at most 2.5? If the answer is a
fraction round UP to the nearest whole number.
a. 16
b. 82
c. 196
d. none of other answers are correct
10. (26.)What are ways to reduce the margin of error?
a. increase the variability in the data
b. decrease the number of observations collected
c. decrease your confidence level
d. none of the other answers are correct
11. (10.)You are measuring the average weight of catsup in catsup bottles ( unknown). You wish to show that the
true average is now different from than the labeled weight. You have information from a random sample of 36
bottles. Assuming the normal distribution requirement is met, what would be the rejection region ( = 0.10)? Reject
Ho if
a. z > 1.645
b. t > 1.69 or t < -1.69
c. F > 3.78
d. F < 2.56
12. (24.)You find that 1.2 points is the difference a typical person’s GPA is from the average of all students in a
university. The previous sentence can be represented with a statistical symbol. What is the symbol?
a. 
b. X
c. s
d. 
13. (11.) You find that the average grade differs among three teaching methods. Under what situation can you say
that changing teaching methods causes the average grade to change?
a. a survey
b. an observational study
c. independent random samples from all people who taken the teaching methods before
d. an experiment
14. (2.)You read that from a telephone survey that it was found that the salary of the average person in Arlington has
increased by $1,000 in the last two years. From what you have learned in this class, what would you need to know to
evaluate the usefulness of the $1000 estimate?
a. nothing more is needed
b. a contingency table
c. the width of the F test degrees of freedom
d. the margin of error
15. (7.)Which of the following is NOT one of basic building blocks of statistics?
a. statistics always gives you correct answers.
b. the typical error of a statistics depends on how many obserations you have collected and on how much variability
you have in the data.
c. sample statistics tend to miss the actual value of parameters.
d. a random sample is needed to reduce bias
16. (13.)Which of the following is a requirement for analysis of variance?
a. the sample data must have the same variance for each value of the data
b. the data must be normally distributed for each population
c. too many formulas and calculations (Hint: no)
d. the factor must be normally distributed
17. (4.)Which of the following is correctly stated?
a. analysis of variance is used when the response is quantitative and the factor is qualitative
b. the chi-square test is used when the response is quantitative and the factor is qualitative
c. a single population assumes that the percent of successes has the same variance.
d. the chi-square test is used when the response is qualitative and the factor is quantitative
18. (23.)If one or more observations are lost in an experiment, you would worry about…
a. the population variances becoming unequal
b. the design becoming unbalanced
c. the population means becoming unequal
d. the sample sizes becoming too large
19. (21.)You have six sections of a class and are measuring the number of passing and the number of failing grades in
each. What procedure would you use?
a. z confidence interval
b. analysis of variance
c. single sample test of a mean
d. chi-square test of equal proportions
20. (1.)Decisions based on either your experience or statistics can be wrong. What is the difference in the two
approaches?
a. Statistics measures the size and chance of an error
b. They tend to have the same size error
c. Experience has a larger chance of getting a correct answer.
d. Statistics is always right.
21. (5.) In analysis of variance, we use an F-test ratio as a test statistic. What do the two components of the F-test
measure?
a. the sum of the squared differences between the observed and the expected counts (divided by the expected counts)
when the two variables are independent.
b. the normality of the variances
c. the variability of the sample means compared to the variation they should have if all means are equal.
d. the degrees of freedom of the contingency table and the degrees of freedom of the variance
22. (15.)You have four ways to teaching new employees data-base. All four are online tutorials. You decide to create
an experiment using students from a university MSIS class. The 28 students in the class are randomly divided into
four sets and a test is given at the end of training. Each set of seven students will complete only one of the four
tutorials. After the experiment, the F-test ratio is calculated to be 1.45. What conclusion can you make about the four
methods?
a. Nothing. We do not know the degrees of freedom
b. We can say that the mean test score differs among the online tutorials.
c. They are all the same
d. We can not say that the mean test score differs among the online tutorials.
23.(28.) In analysis of variance, why do we assume the variation of the population data is the same for all groups?
a. to determine the probability in each cell of the contingency table
b. simplicity
c. reduce bias
d. no particular reason.
24. (19.)The status quo is that the average GPA is the same across colleges. You decide to test this using analysis of
variance. What would be the interpretation of the power of the test?
a. rejecting a true null hypothesis
b. saying the mean GPA have the same variation
c. the level of significance
d. the probability of detecting that at least one of mean GPAs differs from the others, when that is actually the case.
25. (6.)What is the variance of the following population of numbers? 1, 1, 9, 2, 2
a. 9.2
b. 11.5
c. 3.39
d. 5
26. (14.)If you are asking people the letter grade they made on the first two exams (A, B, C, D, and F) and you wish
to see if the grades are related, the degrees of freedom of the test would be
a. 25
b. 16
c. 4 and 12
d. 4
27. (18.)If you determined that differences exist between population means, you would follow this with
a. the Tukey’s procedure
b. a random sample
c. a contingency table
d. a giraffe
28. (25.)If you have 4 random samples each of size 25, the Tukey’s table would use ___ and ____ degrees of
freedom
a. 4 and 96
b. 3 and 96
c. 4 and 100
d. 3 and 100
29. (27.)You are measuring the difference in average salaries between different majors. If the difference between two
sample means was $4 and the Tukey’s margin of error was ± $100,000. You would conclude that
a. there is not an important difference between the average salaries of the two majors and more information is not
needed.
b. the means differ.
c. The first major has a significantly higher mean salary than the other.
d. there might be an important difference between the average salaries of the two majors and more information is
needed.
30.(8.) The empirical rule does NOT require you to have
a. the value of the mean of a population
b. a symmetric mound-shaped population of data
c. the value of the standard deviation of a sample
d. the value of the standard deviation of a population
Answers on next page
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B – see comments below
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Comment on number 26.
Two questions are being asked (a) "What letter grade did you make on the first exam?" and (b)
"What letter grade did you make on the second exam?" This would be a 5 by 5 table. You could
then determine if making an A on the first exam is related to making an A on the second. Same for
the other letter grades.
Many students incorrectly believe that the two questions are (a) " What exam did you take?" and (b)
"What letter grade did you make?". This is a 2 by 5 table but loses information about the
relationship between the letter grades. A 2 by 5 table would allow you to check for the relationship
between the exam and the letter grade and you could discuss which exam had the highest percent of
A's, B's, etc. However you would not know if the same people made A's on both exams or whether
the A's on the first exam became F's on the second.