Download EXAM 1 Practice Problems

BUS/ST 350
EXAM 1 Practice Problems
Material covered: Course Pack: Lecture Unit 1, Lecture Unit 2
WARNING: this sample exam may not cover all the material for which you are responsible!
1.
The heights of American men aged 18 to 24 are approximately symmetric and mound shaped with
mean 68 inches and standard deviation 2.5 inches. Half of all young men are shorter than
a) 65.5 inches b) 68 inches c) 70.5 inches d) can't tell because the median height is not given
2.
Use the information in Problem 1. What percent of young men are taller than 6' 1" ?
a) 94.5% b) 44.5% c) 5.5% d) 2.5%
3.
The grade point averages (GPA) of 7 randomly chosen students in a statistics class are
3.14 2.37 2.94 3.60 1.70 4.00 1.85
The mean GPA for these students is
a) 2.8 b) 2.94 c) 3.6 d) none of the above
4.
Refer to the information given in the previous problem. If !(x  x)# œ 4.51, then the standard
deviation is
a) .75 b) .87 c) .64 d) .80 e) none of the above
5.
A standardized test designed to measure math anxiety has a mean of 100 and a standard deviation
of 10 in the population of first year college students. Which of the following observations would
you suspect is an outlier?
a) 150 b) 100 c) 90 d) all of the above e) none of the above
6.
Which of the following best describes a risk in using the sample range to measure spread?
Choose one of the following:
a) The statistic is not in the same unit of measurement as the observations themselves.
b) The largest or smallest observation may be a mistake or an outlier.
c) It is complicated to compute, which may result in an error.
d) It always produces spreads that are too large.
7.
The distribution represented by the histogram below is:
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Choose one of the following:
a) skewed to the right.
b) skewed to the left.
c) symmetric.
d) normal.
Reiland
BUS/ST 350
Sample Exam 1
page 2
8.
Twenty-eight applicants interested in working for the Food Stamp program took an examination designed to
measure their aptitude for social work. The following test scores were obtained:
79, 93, 84, 86, 77, 63, 46, 97, 87, 88, 87, 92, 68, 72, 86, 98, 81, 70, 66, 98, 59, 76, 68, 91, 94,85, 88, 79.
a. Find the 25th percentile.
b. Construct a boxplot for these observations. Do you observe any outliers?
9.
Two students are enrolled in an introductory statistics course at the University of Florida. The first student
is in a morning section and the second student is in an afternoon section. If the student in the morning
section takes a midterm and earns a score of 76, while the student in the afternoon section takes a midterm
with a score of 72, which student has performed better compared to the rest of the students in his respective
class? For the morning class, the class mean was 64 with a standard deviation of 8. For the afternoon class,
the class mean was 60 with a standard deviation of 7.5.
10. Raw scores on evaluation tests given to elementary school children are often transformed for easier
comparison. A test of reading ability has mean 72 and standard deviation 25 when given to third graders.
So that we can compare third grade scores with “normed” scores of students in other grades, we want scores
in the third grade to have mean 100 and standard deviation 20.
a. What linear transformation will change third grade scores B into new scores B8/A = +  ,B that have the
desired mean and standard deviation? (Use ,  ! to preserve the order of the scores).
b.
Nancy is a third grade student who scored 75 on the test. Find Nancy's transformed score.
11. Which of the following describes a basic DIFFERENCE between nominal data and ordinal data?
a. Nominal and ordinal data are both quantitative data.
b. Nominal and ordinal data are both qualitative data.
c. Nominal data are qualitative data whereas ordinal data are quantitative data.
d. Nominal data have a meaningful zero point and the ratio of the two data values is meaningful
whereas with ordinal data the zero point is arbitrary.
e. Nominal data classify items into one of a set of categories whereas ordinal data classify items
into categories that can be ranked and ordered.
12. Which of the following statements is (are) correct?
a. Histograms and frequency distributions are useful for summarizing ratio data.
b. Histograms and frequency distributions are generally used to summarize the information in vast
amounts of business data.
c. There is greater flexibility in selecting class intervals for histograms than in selecting stems for stemand-leaf plots.
d. Stem-and-leaf plots frequently display the actual data values whereas histograms and frequency
distributions do not.
e. All of the above.
13. A manufacturer of computer hard disk drives knows that its computer hard disk drives have a
mean time to failure of 24 months with a standard deviation of 4 months. The failure data is known to be
symmetric and mound-shaped. Determine the following:
a. What is the approximate proportion of the manufacturer's hard drives that will fail later
than 16 months?
b. What is the approximate proportion of the manufacturer's hard drives that will fail between 16 months
and 28 months?
c. If the manufacturer offers a 20 month warranty on its hard drive, what is the approximate
proportion of these hard drives that could fail under warranty?
14. The following data are a sample of the percentage rates of return experienced by six-month Eurodollar
deposit purchasers:
1 2 2 1 1 4 2 3 1
The standard deviation is:
a. 4 b. 2 c. 1.05 d. 1.11 e. can't be done since some values are negative
BUS/ST 350
Sample Exam 1
page 3
ANSWERS
1. b
2. d (73 inches is how many standard deviations above the mean?) 3. a
6.
The largest or smallest observation may be a mistake or an outlier.
7.
Skewed to the right.
4. b
5. a
8. a. First, order the data from smallest to largest. Since we want the 25th percentile and there are n=28
#&
observations, we compute i œ "!!
(29) œ 7.25; so to find the 25th percentile interpolate between the values in
locations 7 (70) and 8 (72) as follows: U" œ (!  Þ#&Ð(#  (!Ñ œ (!.&!Þ
b.
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46
70.50
No outliers are observed.
9.
84.5
90.25
98
z1 = (76-64)/8 = 1.5 ; z2 = (72-60)/7.5 = 1.6 . The student in the afternoon section performed better.
10. a. 2 equations, 2 unknowns + and , ; (i) new mean must be 100, so we have the equation +  ,Ð(#Ñ œ "!!à
(ii) new standard deviation must be 20 so we have the equation ,Ð25Ñ œ #!. Equation (ii) Ê , œ #!
#& œ .8à
substitute , œ Þ) into equation (i) to get
+ œ "!!  Þ)Ð(#Ñ œ "!!  &(Þ' œ %#Þ%; so the transofrmation is B8/A œ 42.4  .8B .
b. B8/A œ 42.4 + .8Ð(5Ñ œ "!2.4
11. e.
12. e. 13. (use 68-95-99.7 rule) a. .975 b. .815 c. .16 14. b.