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Stat 2160: Exam 1
Fall 2013, Form E
For each of the following questions, select only 1 option and fill the corresponding
bubble on your Scantron. Ensure to read each question carefully.
Name:
Instructor’s name:
1. For each of the following variables, identify the type of variable (categorical vs. numerical).
I. Local name for soft drinks (e.g. Soda, Pop, Coke, etc)
II. Income tax brackets (e.g. Below $8925, $8925-36250, $36250-$87850, etc)
A. I. Numeric , and II. Categorical
B. I. Categorical , and II. Numeric
C. There is no correct match.
D. I. Categorical , and II. Categorical
E. I. Numeric , and II. Numeric
2. Choose the description which best describes the shape of this boxplot.
A. Uniform
B. Right-skewed
C. Bimodal
D. Left-skewed
E. Contaminated
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3. The following table gives the five-number summary for a dataset on Temperature. Using this
output; calculate the inter-quartile range (IQR).
A. 119.2
B. 51.6
C. 74.7
D. 87.2
E. -51.6
4. The following table gives the five-number summary for a dataset on Temperature. Using this
output; calculate the percent of values between 0.3 and 85.9.
A. 75%
B. 50%
C. 0%
D. 25%
E. 100%
5. Google’s stock (GOOG) was tracked for 10 days showing closing prices of 857.6; 828.25; 832.29;
867.12; 847.29; 851.65; 817.79; 830.55; 840.82; 862.1. Calculate the standard deviation of the
dataset.
A. 844.055
B. 843.546
C. 15.4193
D. 16.2534
E. 8,435.46
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6. Suppose that the middle 68% of families of a certain demographic monthly food expenditures
fall between 293.45 and 315.73. Give an approximate estimate of the standard deviation of the
expendiutes. Assume the expenditures have a normal distribution.
A. 22.28
B. 304.59
C. 11.14
D. 5.57
E. -11.14
7. Imagine that Exam 1 for Statistics 2160 this term will have 62 questions. Each question has
5 multiple choice options, giving you a probability of 0.2 of getting each question right purely
by guessing. Assuming that you guess on all questions, what is the probability that you get
greater than 15 questions right on your exam?
A. 0.085
B. 0.0425
C. 0.1619
D. 0.2469
E. 0.8381
8. Apple’s market share in the smart phone market represents a proportion of 0.1835. If Apple
conducts a survey nationwide of 641 smart phone users, what is the probability that greater
than 127 of the people are Apple users?
A. 0.182
B. 0.0252
C. 0.8432
D. 0.0126
E. 0.1568
9. When rolling a fair die 195 times, what is the probability of rolling a 6 greater than 25 times?
A. 0.0859
B. 0.014
C. 0.9421
D. 0.028
E. 0.9141
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10. Suppose that the probability of a baseball player getting a hit in an at bat is 0.2807. If the
player has 38 at bats during a week, what’s the probability that he gets greater than 9 hits?
A. 0.7797
B. 0.0625
C. 0.125
D. 0.6547
E. 0.3453
11. Suppose that the mean and standard deviation of the scores on the mathematics portion of the
SAT are 494.87 and 66.717, respectively, for a given year. 14.68% of students scored greater
than what score? Assume the distribution is approximately normal.
A. We do not have enough information to calculate the value.
B. 564.9
C. 4,180
D. 5,169.7
E. 424.8
12. Suppose that the mean and standard deviation of the number of gallons of milk sold at a local
supermarket per day are 190.911 and 10.5737, respectively. Fill in the blank: the supermarket
will sell less than $
gallons of milk on 34.36% of days. Assume the distribution is
approximately normal.
A. 186.65
B. 145.89
C. 235.93
D. 195.17
E. We do not have enough information to calculate the value.
13. The stock price for International Business Machines (IBM) historically has followed an approximately normal distribution (when adjusting for inflation) with a mean of $150.402 and
standard deviation of $4.1793. What is the probability that on a selected day the stock price
is below $146.72?
A. 0.8284
B. We do not have enough information to calculate the value.
C. 0.8108
D. 0.1892
E. 0.1716
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14. Suppose that the distribution of income in a certain tax bracket is approximately normal
with a mean of $31,545.33 and a standard deviation of $4,603.163. Approximately 64.64% of
households had an income greater than what dollar amount?
A. 33,274.37
B. 7,990,583
C. We do not have enough information to calculate the value.
D. 7,927,492
E. 29,816.29
15. Suppose that the scores of golfers on the PGA tour have a mean of 67.15 and a standard deviation of 3.084. A random sample of 30 is taken from the population. What is the distribution
of the sample mean?
A. Approximately normal with mean 12.26 and standard error 0.56.
B. 67.15 give or take 3.084.
C. 68% of sample averages will fall between 64.07 and 70.23.
D. Approximately normal with mean 67.15 and standard error 0.56.
E. Approximately normal with mean 67.15 and standard error 3.084.
16. Suppose you are interested in measuring the amount of time on average it takes you to make
your commute to school. You’ve estimated that the average time is 38.4 minutes with a standard
deviation of 5.362 minutes. Over 12 random days, you measure your commute time. Assuming
that your estimated parameters are correct, what is the probability that the average commute
time over that 12 day period is greater than 36.19 minutes?
A. 0.907
B. 0.0767
C. 0.9233
D. 0.6599
E. 0.3401
17. Suppose that NBA players average 22.41 points per game with a standard deviation of 9.212.
A random sample of 57 players is taken. There is a 91% chance that the average points per
points.
game is less than $
A. 20.77
B. 34.76
C. 10.06
D. There is not enough information to determine this.
E. 24.05
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18. In a recent survey of 102 WMU graduates, 36 students said that parking was too limited on
campus. What is the estimate of the population proportion? What is the standard error of
this estimate?
A. The true population proportion is needed to calculate this.
B. Estimate of proportion: 0.647. Standard error: 0.04732.
C. Estimate of proportion: 0.647. Standard error: 0.004685.
D. Estimate of proportion: 0.353. Standard error: 0.04732.
E. Estimate of proportion: 0.353. Standard error: 0.004685.
19. Suppose that 22.24% of all vehicles on the road get a fuel economy of at least 35 miles per
gallon(MPG). You conduct an observational study on a stretch of road outside of campus and
record the make and model of 796 vehicles over a month long period. What is the probability
that less than 21.34% of the cars you observed get at least 35 MPG?
A. 0.7292
B. 22.46
C. 0.2708
D. 0 .5
E. 8.591e-67
20. A sample proportion is calculated from a sample size of 201. How large of a sample would we
need in order to decrease the standard error by a factor of 7?
A. 402
B. 1,407
C. 9,849
D. 2,010
E. 532
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