Stat 207: Midterm-1 (Version A)
University of Dammam
Date: Wednesday, March 20, 2013
Duration: 60 minutes.
Instructor: Dr. Nahid Sultana
Name:______________________________________________________________________
Student ID Number: ___________________Solution______________________________
Group: _____________________________________________________________________
Instructions:
This test consists of 15 multiple choice questions worth 1 mark each (no part marks). The
questions must be answered on the computer card with an HB PENCIL.
YOU ARE RESPONSIBLE FOR ENSURING THAT YOUR COPY OF THE PAPER IS
COMPLETE. BRING ANY DISCREAPANCIES TO THE ATTENTION OF THE INVIGILATOR.
Only standard calculator (ex. the Casio fx 991) is permitted.
Computer Card Instructions:
NOTE: IT IS YOUR RESPONSIBILITY TO ENSURE THAT THE ANSWER SHEET IS
PROPERLY COMPLETED: YOUR EXAMINATION RESULT DEPENDS UPON PROPER
ATTENTION TO THESE INSTRUCTIONS
The scanner, which reads the sheets, senses the shaded areas by their non-reflection of light.
A heavy mark must be made, completely filling the circular bubble, with an HB pencil. Marks
made with a pen or felt-tip marker will NOT be sensed. Erasures must be thorough or the
scanner may still sense a mark. Do NOT use correction fluid on the sheets. Do NOT put any
unnecessary marks or writing on the sheet.
1. Print your name, student number, Section (group), and course name in the space
provided at the top of the form and fill in the corresponding bubbles underneath. Fill in
the bubble corresponding to the version number of your test.
2. Mark only ONE choice from the alternatives (A,B,C,D,E) provided for each question.
3. Make sure that the number of the question on the scan sheet is the same as the
question number on the test paper.
4. Pay particular attention to the Marking Directions on the form.
5. Begin answering questions using the first set of bubbles, marked "1".
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Stat 207, Midterm-1, Term-2, 2013
1. The figure below is a histogram of the lengths of words used in Shakespeare's plays.
Because there are so many words in the plays, we use a histogram of percents.
What is the overall shape of this distribution?
A. Normal
B. Skewed right
C. Skewed left
D. Bimodal
2. Which of the following variables is categorical?
A. The number of Facebook friends you have.
B. Amount of time a student spends on the internet in one day.
C. Available food choices in the student cafeteria.
D. None of the above.
3. The length of human pregnancies from conception to birth varies according to a
distribution that is approximately normal with mean 266 days and standard deviation 16
days. Between what values do the lengths of the middle 95% of all pregnancies fall?
A. 234 days and 298 days
B. 250 days and 282 days
C. 266 days and 298 days
D. None of the above
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Stat 207, Midterm-1, Term-2, 2013
4. Find the value z of a standard normal variable Z that satisfies each of the following
conditions. (Use the z-score from the table that comes closest to satisfying the
condition.) 44% of the observations fall above z
A. 0.28774
B. 0.67003
C. -0.15097
D. 0.15097
5. Statistics were gathered on the number of homicides committed with guns in Australia in
the years from 1980 to 2004. From these data the following graph was constructed:
This plot is a graph of a(n) _____________ and it shows that there is(are) ___________
in the data.
A. categorical variable; skewness to the right
B. histogram; multiple peaks
C. line; an increasing trend
D. time series; a decreasing trend
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Stat 207, Midterm-1, Term-2, 2013
6. A researcher reports that, on average, the participants in his study lost 10.4 lbs after two
months on his new diet. A friend of yours comments that she tried the diet for two
months and lost no weight, so clearly the report must be a fraud. Which of the following
statements is correct?
A. Your friend must not have followed the diet correctly because she did not lose
weight.
B. Because your friend did not lose weight, the report must not be correct.
C. The report gives only the average. This does not imply that all participants
in the study lost 10.4 lbs or even that all participants lost weight. Your
friend's experience does not necessarily contradict the study results.
D. In order for the study to be correct, we must now add your friend's results to
those of the study and recompute the new average.
7. Volunteers for a research study were divided into three groups. Group 1 listened to
Western religious music, Group 2 listened to Western rock music, and Group 3 listened
to Chinese religious music. The blood pressure of each volunteer was measured before
and after listening to the music, and the change in blood pressure (blood pressure
before listening minus blood pressure after listening) was recorded.
What could we do to explore the relationship between type of music and change in
blood pressure?
A. See if blood pressure decreases as type of music increases by examining a
scatterplot.
B. Make a histogram of the change in blood pressure for all of the volunteers.
C. Make side-by-side boxplots of the change in blood pressure, with a
separate boxplot for each group.
D. Do all of the above.
8. A(n) ____ is an observation that is substantially different from the other observations.
A. lurking variable
B. Outlier
C. confounding variable
D. None of the above.
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Stat 207, Midterm-1, Term-2, 2013
9. The New England Patriots are a top ranked team in the National Football League (NFL)
and the Saskatchewan Roughriders are the 2007 champions of the Canadian Football
League (CFL). From the 2007 rosters of these two teams, the weight of the players was
determined and the following side-by-side boxplots of their weights is provided below:
Which of the following statements about these side-by-side boxplots is (are) TRUE?
A. The weights of the New England team exhibit less overall variation than the
Saskatchewan team.
B. The median weight for the Saskatchewan team is higher than the median weight
for the New England team.
C. The median weight for the New England team is higher than the median
weight for the Saskatchewan team.
D. The IQR for the Saskatchewan team is greater than the IQR of the New England
team.
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Stat 207, Midterm-1, Term-2, 2013
10. In the National Hockey League a good predictor of the percentage of games won by a
team is the number of goals the team allows during the season. Data were gathered for
all 30 teams in the NHL and the scatterplot of their Winning Percentage against the
number of Goals Allowed in the 2006/2007 season with a fitted least-squares
regression line is provided:
The least-squares regression line and r 2 were calculated to be
Winning Percent (%) = 116.95 – 0.26 Goals Allowed
r 2 = 0.69
For the Winning Percent and Goals Allowed least-squares regression analysis above, which of
the following statements is (are) TRUE?
A. About 69% of the variation in the variable Goals Allowed can be explained by the leastsquares regression of Winning Percent on Goals Allowed.
B. About 69% of the variation in the variable Winning Percent can be explained by
the least-squares regression of Winning Percent on Goals Allowed.
C. If the correlation between Winning Percent and Goals Allowed were calculated it would
be 0.83.
D. A and C are true.
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Stat 207, Midterm-1, Term-2, 2013
11. The 94 students in a statistics class are categorized by gender and by the year in
school. The numbers obtained are displayed below:
The data are going to be summarized by computing the conditional distributions of year
in school for male and female students. What would be the entry for male sophomores?
A. 0.065
B. 0.105
C. 0.33
D. 2
12. A researcher is planning to carry out a sample survey in order to estimate the proportion of
people in a very large population of interest who have shopped online in the previous 6
months. A simple random sample is to be selected but there is debate about whether to
select an SRS of size 500 or of size 1000. With respect to the sample proportion, which
statement best describes what can be expected to happen using these two different sample
sizes?
A. The statistic will be more biased in the sample of size 500, but the variability of the
statistic will be smaller.
B. Using the larger sample size will reduce the bias of the statistic, but the spread of
the sampling distribution will be greater.
C. The statistic from either sample size will be unbiased, but the sampling distribution of
the statistic from the sample of size 1000 will show greater variability.
D. The statistic from either sample size will be unbiased, but the sampling
distribution of the statistic from the sample of size 1000 will show less
variability.
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Stat 207, Midterm-1, Term-2, 2013
13. A scatterplot of a variable y versus a variable x produced the scatterplot shown below.
The value of y for all values of x is exactly 1.0.
What do we know about the correlation between x and y?
A. It is +1 because the points lie perfectly on a line.
B. It is either +1 or –1, because the points lie perfectly on a line.
C. It is 0 because y does not change as x increases.
D. None of the above.
14. A baseball enthusiast believes pitchers who strike out a lot of batters also walk a lot of
batters. He reached this conclusion by going to the library and examining the records of
all major league pitchers between 1990 and 1995. What type of study is his decision
based on?
A. Anecdotal evidence.
B. An observational study based on available data.
C. An observational study based on a sample survey.
D. An experiment.
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Stat 207, Midterm-1, Term-2, 2013
15. A researcher is studying the relationship between sugar consumption and weight gain.
Twelve volunteers were randomly assigned to one of two groups. The first group of five
participants was put on a diet low in sugar and the second group of the remaining seven
participants received 10% of their calories from sugar. After 8 weeks, weight gain was
recorded from each participant.
Each of the 12 volunteers receives a label: 01 through 12. Use the list of random digits
below to determine the labels of the first five participants selected who were put on a
low-sugar diet. Start at the beginning of the list and use double-digit labels.
81507 27102 56027 55892 33063 41842 81868 71035 09001 23367 49497
A. 8, 1, 5, 0, 7
B. 8, 1, 5, 7, 2
C. 2, 6, 10, 9, 12
D. 2, 2, 6, 10, 9
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