Download STA 2023- SPRING 2012 RIPOL

STA 2023- SPRING 2012
RIPOL
EXAM 1 Test Form Code A
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Instructions:
This exam contains 33 Multiple Choice questions. Please select the best answer among the alternatives given. Each
question is worth 3 points, for a total of 99 points. One point will be given for correctly bubbling in the scantron your
personal information and test form code.
You may write whatever you want on this test, but only the answers bubbled in the scantron sheet will be graded.
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Questions 1 – 6 The following is an excerpt from an article from parade.com
A study in the journal Archives of Disease in Childhood came to the following conclusion: Active children fall asleep
faster and sleep longer than children who get less exercise. The researchers followed nearly 600 New Zealand 7-yearolds. They had the parents answer a questionnaire on their children’s sleeping habits. They also had the kids wear
monitors around their waists over one 24-hour period to measure their activity levels each minute of the day. Here’s
what the study found: It took an average of 26 minutes for a child to fall asleep. But for every hour a youngster was
inactive during the day, it took three minutes longer.
Poor sleep habits have been associated with behavioral problems, low grades in school, and even an increased risk of
being overweight. The study, the authors noted, “emphasizes the importance of physical activity for children, not only
for fitness, cardiovascular health, and weight control, but also for sleep.” It seems logical that kids who run around all
day are more tired and therefore sleep better. But consider: Perhaps it’s the other way around. Maybe children who get a
lot of sleep have more energy to run around all the time.
1. This is an example of:
a) a census
c) a matched pairs design
b) an observational study
d) an experiment
Match the following, as they relate to the study:
___ 2. response variable
a) 600
___ 3. explanatory variable
b) - 3
___ 4. experimental units
c) 26
___ 5. slope of the line
d) time to fall asleep
e) activity level
6. The last line of the article illustrates which of the following statistical issues:
a) Simpson’s Paradox
b) independence
c) disjoint events
d) misuse of cause and effect
e) response bias
7. You stick your hand in a box of lego’s and select 5 of them. Is this a random sample?
a) Yes – we are using a mechanical method.
b) Yes – lego pieces are not able to move.
c) No – it’s biased towards the bigger pieces.
d) No – this would be a voluntary sample.
Questions 8 – 11 Students in an Honors Statistics class were asked how many hours a day they spend on Facebook.
The following is a stemplot created in Minitab from their responses.
8. The mode of this distribution is ____ hour(s).
a) 8
b) 1.5
c) 16
d) 1
9. The IQR of this distribution is _____ hour(s).
a) 2
b) 1
c) 2.5
d) 0
10. The shape of this distribution is:
a) bell shaped with an outlier
b) skewed left
c) skewed right
d) bimodal
11. Interpreting this stemplot is an example of:
a) descriptive statistics
b) inferential statistics
c) designing a study
d) statistical probability
e) 0
e) 1.5
Stem-and-leaf of facebook-time
Leaf Unit = 0.10
3
9
(16)
22
19
11
11
3
3
1
1
1
1
1
1
1
1
0
0
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
N
= 47
022
555555
0000000000000000
555
00000000
00000000
00
0
Questions 12 – 14 Students in an Honors Statistics class were asked: Would you “friend” / have you “friended” your
parents in Facebook? The results appear on the table below.
no
yes
all
12. What percentage of students in the sample would “friend” their parents?
male
6
10
16
a) 29/45
b) 32/45
c) 22/29
d) 22/32
female
7
22
29
all
13
32
45
13. What percentage of females would “friend” their parents?
a) 29/45
b) 32/45
c) 22/29
d) 22/32
14. What percentage of students who would “friend” their parents are female?
a) 29/45
b) 32/45
c) 22/29
d) 22/32
Questions 15 - 18 The distribution of weights for pure bred adult Chihuahua dogs is approximately Normal with a
mean of 4 pounds and a standard deviation of 1.2 pounds.
15. What percentage of pure bred adult Chihuahua dogs will weigh more than 3.5 pounds?
a) 42%
b) 66%
c) 58%
d) 34%
16. What is the weight of the largest 3% of all pure bred adult Chihuahua dogs?
a) 5.88 lbs
b) 2.12 lbs
c) 6.26 lbs
d) 1.74 lbs
17. What percentage of all pure bred adult Chihuahua dogs weigh between 2.8 and 5.2 pounds?
a) 50%
b) 65%
c) 68%
d) 71%
18. What is the lower quartile of the distribution of weights of pure bred adult Chihuahuas?
a) 3.33 lbs
b) 3.20 lbs
c) 4.67 lbs
d) 4.80 lbs
Questions 19 - 22 (Homework # 6.43) The juror pool for the upcoming murder trial of a celebrity actor contains the
names of 100,000 individuals in the population who may be called for jury duty. The proportion of the available jurors
on the population list who are Hispanic is 0.40. A jury of size 12 is selected at random from the population list of
available jurors. Let X= the number of Hispanics selected to be jurors for this jury.
19. What is the distribution of X?
a) Bimodal (0.4, 0.6)
b) Binomial (12, 0.4)
c) Normal (4.8, 1.7)
d) Uniform (0, 12)
20. Find the probability that no Hispanic is selected.
a) zero
b) 0.98259
c) 0.99782
d) 0.01741
e) 0.00218
21. Find the probability that exactly one Hispanic is selected.
a) zero
b) 0.98259
c) 0.99782
d) 0.01741
e) 0.00218
22. Find the probability that at least one Hispanic is selected.
a) zero
b) 0.98259
c) 0.99782
d) 0.01741
e) 0.00218
23. Here are the weights, in ounces, of 6 Labrador Retriever puppies from the same litter. Find the standard deviation.
15.7 14.9 14.5
13.8 15.1 14.7
a) .6338
b) .6162
c) .6062
d) .5786
Questions 24 – 25 Airplane flights from San Francisco to 20 different locations around the world were selected, and
their flight times, in minutes, were used to create the boxplot below.
24. Twenty five percent of the flights lasted approximately between:
a) 50 and 125 minutes
b) 125 and 250 minutes
c) 250 and 325 minutes
d) 325 and 850 minutes
e) all of the above
25. The mean of this distribution:
a) is approximately 250 minutes
b) is less than 250 minutes
c) is more than 250 minutes
d) is impossible to tell
26. A z-score:
a) measures how many standard deviations above or below the mean an observation is.
b) follows a Normal distribution that can be written as Z~N(1,0).
c) helps us find probabilities for any continuous random variable.
d) all of the above
e) none of the above
Questions 27 – 33 Can we predict the cost of an airplane flight based on the distance from its destination? Commercial
non-stop flights from San Francisco, California, to 20 different locations around the US and the world were selected.
The distance (in miles) and cost (in dollars) were recorded for each one, and used to perform a regression analysis.
27. The correlation between cost and miles for this
data is:
a) .904
b) .807
c) .719
d) .667
Fitted Line Plot
cost = 51.72 + 0.2150 miles
1800
S
R-Sq
R-Sq(adj)
1600
1400
1200
cost
28. Use the regression equation to predict the cost of a
flight to Gainesville, 2350 miles away.
a) $2150
b) $1215
c) $517
d) $557
181.162
81.7%
80.7%
1000
800
600
400
29. One of the flights in the study was from San
Francisco to Sydney, Australia, 7412 miles away, at a
cost of $1481.50. What is the residual for this point?
a) -2351
b) -250
c) -164
d) -3710
200
0
0
1000
2000
3000
4000
miles
5000
6000
7000
8000
30. If we redo the regression analysis using only flights of 3000 miles or less, how would the results change compared
to the ones using all the data?
a) R2 and r would both be weaker
b) R2 would be weaker, but r would be stronger
2
c) R and r would both be stronger
d) R2 would be stronger, but r would be weaker
31. If we truly are interested in flights that go distances over 3000 miles, the best thing to do would be to:
a) interpret the results of the analysis presented above.
b) conduct a non-linear regression that would fit the data better.
c) eliminate the outliers, and then re-analyze the data.
d) collect more data on long-distance flights.
e) all of the above.
32. Which of the following is the best interpretation of the slope of the line:
a) As the length of the trip increases by 1 mile, its cost increases by $51.72 on average.
b) As the length of the trip increases by 1 mile, its cost increases by $0.2150 on average.
c) As the cost of the trip increases by $1, its length increases by .5172 miles on average.
d) As the cost of the trip increases by $1, its length increases by 21.50 miles on average.
33. Which of the following is the best interpretation of the y-intercept of this line?
a) Even though there are no free flights, 0.5172 miles is the minimum distance predicted for any flight.
b) Even though there are no free flights, 0.2150 miles is the minimum distance predicted for any flight.
c) Even though there are no flights of zero miles, $51.72 is the minimum price predicted for any flight.
d) Even though there are no flights of zero miles, $21.50 is the minimum price predicted for any flight.