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Exam 1 Version ANameRecitation Day&Time

STAT 1450 Exam 1 Autumn 2013 - Version A

Circle your recitation TA’s name from the list of names below:

Andrew Bean Thomas Kilbane Mark Risser Hui YangMatt Brems Angus McKay Andrew Olsen

Your percentage score will be based upon 50 points.

**Multiple Choice** (2 points each) Circle the best answer.Use the following information for Questions 1-4: A new flu vaccine was administered in a small community in early fall. Some received one shot,some two, and others declined the vaccine. The 1,000 participants’ physicians were contacted thefollowing spring and asked if their patients had contracted the flu over the 6-month period. The

results have been summarized in the following table. Contraction of FluNumber of Vaccines Yes No Total

None 24 289 313One 9 100 109Two 13 565 578

Total 46 954 1000

1) What percent of all participants neither contracted the flu nor had a vaccine?a) 52.2%

b) 28.9%c) 7.7%

d) 2.4%

2) What percent of people who declined the vaccine, eventually contracted the flu?a) 52.2%

b) 28.9%c) 7.7%d) 2.4%

3) Approximately, what percent of recipients of two vaccines contracted the flu?a) More than 50%

b) About 25%c) About 10%

d) About 2%

4) Which is most appropriate in determining if there is an association between the variable presented inthis two-way table?

a) Marginal distributions of ‘contraction of flu.’ b) Marginal distributions of ‘number of vaccines.’c) Conditional distributions of participants who did not contract the flu.d) Conditional distributions for each of the numbers of vaccines administered.

Exam 1 Version A



Exam 1 Version A

5) Stemplots are used for which creating graphical displays of these types of variables?a) Quantitative.

b) Semi-modal.c) Qualitative.d) Categorical.

6) Chicago is now rivaling Detroit for having the largest number of homicides in the United States. Itturns out that the month with the largest murder rate in 2012 (July 2012) was underreported. How willrecording the correct value impact the mean and standard deviation?

a) The mean will increase, the standard deviation will increase. b) The mean will decrease, the standard deviation will decrease.c) The mean will increase, the standard deviation will decrease.d) The mean will decrease, the standard deviation will increase.

7) Referring to the exercise from above, which of the following options would bestestimate the z-score from July 2012?

a) 0.00 b) -2.00.c) +2.00.d) 18.6 per 1000 residents

8) The time it takes a randomly selected new employee to perform a certain task is normally distributedwith a mean value of 120 seconds and a standard deviation of 20 seconds. Which of the followingintervals contains approximately 95% of times (in seconds)?

a) (60, 180)

b) (80, 160)c) (100, 140)d) (80, 180)

9) In regression, which of the following must be true about a data value that has a positive residual?a) The mean is larger than the median.

b) The observed value of the response is larger than the value predicted by the regression line.c) The value predicted by the regression line is larger than the observed value of the response.d) The value is an influential observation.

10) Consider the following potential survey question: “Given his large fan base, international acclaim,and ‘swagger,’ would you consider attending an upcoming ‘Drake’ concert at the Schottenstein Center?” This question is:

a) biased toward respondents saying “no.” b) biased toward respondents saying “yes.”c) unbiased.d) symmetric

Exam 1 Version A



Exam 1 Version A

***For Questions 11-14, you cannot get full credit unless you show your work. Partial credit will begranted based on worked shown. Make sure to show formulas and calculator inputs whereappropriate. Explanations should include relevant computations and appropriate statisticalreasoning.

6 pts. total

11) The following histogram, boxplot, and summary statistics are for the numbers of homicides fora Detroit neighborhood.

# of Homicides

5 pts.

a) A member of the Mayor’s staff would like you to describe the data. Be sure that yourdescription references at least 3 of the features commonly associated with data; and that eachfeature cited has at least 1 supporting numerical measurement.

1 pt.

b) Compute the interquartile range.

1

2

C o u n t

5 10 15 20 25 30 35 40

100.0% maximum 3799.5% 3797.5% 3790.0% 34.975.0% quartile 2650.0% median 17.525.0% quartile 13.2510.0% 92.5% 90.5% 90.0% minimum 9

Mean 19.416

Std Dev 8.575Std Err Mean 2.47551

Upper 95% Mean 24.865

Lower 95% Mean 13.9681

N

Exam 1 Version A



Exam 1 Version A6 pts. total

12) A flu vaccination study was referenced earlier in this exam. As a STAT 1450 student, you have been invited to be a member of the research team. In this study, 100 subjects are randomlyassigned this fall. They will receive either the new vaccine or a placebo from a set of physicians.Flu incidence rates will be compared in the spring.

2 pts.

a) The research team would like to know more about “double-blind” experiments.Explain what a “double-blind” experiment is in the context of this study.

4 pts.

b) You now believe that a lurking variable might confound the results.Answers may vary, but identify a potential lurking variable here -> _________

Create a diagram of the experiment.Be sure to include the subjects, “blocks”, treatments, and the response that is to be measured.

5 pts. total

13) Earlier in the exam it was mentioned that the time it takes a randomly selected new employee to perform a certain task is normally distributed with a mean value of 120 seconds and a standarddeviation of 20 seconds.

3 pts. 2pts.

a) What proportion of new employees b) Employees who complete the taskneed longer than 149 seconds to in the bottom 4% are candidates for

perform the task? a bonus. What time qualifiessomeone for a bonus?

Exam 1 Version A



Exam 1 Version A

An optional exercise….3pts.

A new professional on the golf tour, Tiger Nicklaus , plays best on short holes.When facing a Par-3 hole his distribution is:

# of strokes 2 3 4 5 probability .12 .80 .06 .02

a) What are the two elements that makes b) How likely is it that hethis a “probability model?” does not hit the ball

into the hole in three strokes?

Select Formulas

Sample Variance: Slope of a Regression Line:

2 2

1

1( )

1

n

ii

s x xn =

= −−

∑ y

x

sb r

s=

Exam 1 Version A



Exam 1 Version A

Exam 1 Version A

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