Download Exam 2

Exam 2
1.
2.
3.
Name:
Load the data set physicians.xls. The data show the number of physicians of each sex working in
each specialty. Construct a scatterplot of Women versus Men. Which specialty is an outlier?
(a.)
dermatology
(b.)
pediatrics
(c.)
plastic surgery
(d.)
radiology
Open the data set planets.xls. Construct a scatterplot of Revolution versus Distance. Describe
the direction, strength, and form of the association.
(a.)
positive, moderate, linear
(b.)
negative, moderate, linear
(c.)
positive, strong, nonlinear
(d.)
no relationship
Calculate the correlation between Revolution and Distance.
(a) -.02
(b) .55
(c) .99
(d) -55
4.
Which of the following is NOT true about correlation?
(a.)
it is only appropriate to use correlation when the relationship is linear
(b.)
if the correlation coefficient is close to 1 or -1, there is a cause-and-effect relationship
(c.)
correlation is sensitive (not resistant) to outliers
(d.)
all of the above are true
5.
6.
7.
Sampling variability is the concept that the results in a study will vary from sample to
sample in random sampling. To reduce sampling variability, a researcher can…
(a.)
increase the sample size
(b.)
use resistant parameters
(c.)
make a dotplot
(d.)
use judgment instead
The best possible procedure for using a sample for estimating a characteristic of a
population is one that has:
(a.)
High bias and low variability (b.)
Low bias and low variability
(c.)
Low bias and high variability (d.)
High bias and high variability
Below is the Statcrunch output for a linear regression.
Simple linear regression results:
Dependent Variable: SUGAR(mg)
Independent Variable: SODIUM(mg)
SUGAR(mg) = 13579.683 - 29.000984 SODIUM(mg)
Sample size: 20
R (correlation coefficient) = -0.453
R-sq = 0.20525242
The slope of the regression equation indicates that…
8.
(a)
There is a strong negative linear relationship
(b)
There are 13,580 mg of sodium for every gram of sugar
(c)
An increase of 1 mg of sodium tends to go with a decrease in 29 mg of sugar.
(d)
None of the above
The “line of best fit” under the least squares criterion is the one which…
(a)
minimizes the sum of all the perpendicular distances from the points to the line.
(b)
has the greatest sum of squared errors in predictions.
(c)
has the smallest sum of squared residuals
(d)
has the smallest average residual
9.
It may be necessary to transform the data such as by computing logs or square roots on
before performing a linear regression if…
(a)
(b)
(c)
(d)
there are many outliers
the scatterplot shows a nonlinear relationship
there is no apparent relationship between the variables
all of the above
Consider the two-way table below based on a a class of 30 students and their responses as to
whether or not they own a cat and whether or not they own a dog:
10.
Total
Has a Dog
8
4
12
No Dog
2
16
18
Total
10
20
30
80%
40%
33%
50%
What proportion of students who own a cat also own a dog?
(a.)
(b.)
(c.)
(d.)
12.
No Cat
What proportion of students own a cat?
(a.)
(b.)
(c.)
(d.)
11.
Has a Cat
80%
40%
33%
67%
What proportion of students who own a dog also own a cat?
(a.)
(b.)
(c.)
(d.)
80%
40%
33%
67%
13.
Describe the relationship between having a cat and having a dog in this class.
(a.) whether a student has a dog is not related to whether the student has a cat
(b.) Students with a cat are more likely to also have a dog than students without a cat
(c.) Students with a dog are less likely to have a cat than students who do not have a dog
(d.) Most students have either a cat or a dog or both
14. Based on the segmented bar graph, the proportion
of Women who prefer Dance is about…
(a.)
11%
(b.)
20%
(c.)
50%
(d.)
64%
15. The proportion of Men who prefer Sports is
about…
(a.)
10%
(b.)
20%
(c.)
50%
(d.)
70%
16.
The following data is based on a survey of students' smoking habits taken in eight
Arizona high schools comparing smoking and nonsmoking teens based on whether both
parents, one parent or neither parent is a smoker:
smoker
non smoker
Total
both parents smoke
400
1380
1780
one smokes
416
1823
2239
neither smoke
188
1168
1356
1004
4371
5375
Total
Use the pie charts below to decide which of the following is NOT true about the
relationship between whether a teen smokes and whether both, one, or neither of their
parents smoke.
(a.) Non-smokers are more likely to have parents who both do not smoke than smokers
(b.) Both smokers and non-smokers have about just as likely to have one parent who
smokes
(c.) Non-smokers parents are usually non-smokers
(d.) Smokers are more likely to have parents who both smoke than non-smokers
SMOKERS
NON-SMOKERS
17.
Characteristics of a population are called ________, while those of a
sample are termed _________.
(a.) statistics; measures
(b.) parameters; statistics
(c.) statistics; variables
(d.) statistics; parameters
18.
Suppose we are interested in the average math PSSA scores for Haverford High School
juniors. The set of all juniors at Haverford High School would comprise the ________
while the set of all juniors in Mr Peterson’s block 3 class is a __________.
(a.) statistic; sample
(b.) sample; parameter
(c.) statistic; parameter
(d.) population; sample
19.
In a study of eating habits among Haverford High School teachers it was determined that
80% of ALL teachers prefer pizza to tacos. In a second study using a random sample of
teachers, 50% of the teachers in the sample preferred pizza to tacos. The number 50% is
a _________ while 80% is a _________.
(a.) statistic; sample
(b.) sample; parameter
(c.) statistic; parameter
(d.) population; sample
Below is a list of names numbered 1 to 20. Use the random number table to randomly select 5
names from the list by starting at the beginning of the table and taking pairs of digits.
1
Sofia
11
Dara
2
Eassa
12
Jay
3
Jeffrey
13
Nicole
4
Shakoya
14
Francis
5
John
15
Audrey
6
Rebecca
16
Anthoula
7
William
17
Hiep
8
Johanna
18
Sean
9
Allyson
19
Shanira
10
Brandon
20
Alexis
Table of random digits
11121 61998 32134 10012
99091 67743 11123 45672
04567 00998
20.
What is the second name selected?
(a.) Nicole
(b.) Jeffrey
(c.) Jay
(d.) Allyson
21.
What is the fifth name selected?
(a.) Nicole
(b.) Jeffrey
(c.) Jay
(d.) Allyson
22.
Which of the following is really a simple random sample?
(a.) The teacher wants to show a representative sample of student work, so she picks one
good paper, one average paper, and one bad paper.
(b.) The gym teacher asks the students to line up and count off by four’s. All the “one’s”
are selected to be one team.
(c.) The name of each person in the population is put into a hat and mixed well. Names
are drawn from the hat without looking.
(d.) The surveyor picks a sample of people he feels is representative of the population.
23.
A grocer receives a shipment of apples in a large crate. In order to determine the
proportion of apples that are bruised in the large crate of apples, she examines a sample
of 20 apples taken from the top of the crate and notes that 5% are bruised. The sampling
method could be said to be biased because…
(a.) the apples in this crate may have been damaged during shipment
(b.) this crate of apples may not be representative of all such crates
(c.) she only looked at 20 apples, her sample is too small
(d.) the proportion of apples that are bruised in the sample using only top apples is likely
to be smaller than the proportion of apples that are bruised in the entire crate.
24.
An experiment is conducted to determine if the use of certain specified amounts of a drug
will increase IQ scores. In this study, IQ serves as:
(a) an explanatory variable
(b) a moderator variable
(c) a response variable
(d) a control variable
25.
In order to test the effects of light level on student performance on tests, subjects are
randomly assigned to two rooms to take a test. One room had a lower light level than the
other. During the testing it was noted that one room’s temperature was 70 degrees
whereas subjects in the other group are simultaneously tested in a nearby identically
appointed room with the heat set at 60 degrees. A possible confounding variable in this
study is…
(a.) test score
(b.) lighting level
(c.) temperature
(d.) random assignment
26.
Researchers would like to understand how pet ownership is related to longevity. Which
of the following is true?
(a.) This study would be considered an observational study if they randomly assigned
subjects to either receive a pet or not.
(b.) This study would be considered an experiment if they randomly assigned subjects to
either receive a pet or not.
(c.)This study would be considered an experiment if they took a random sample of pet
owners and noted whether or not they owned a pet
(d.) none of the above is true
27.
If the researchers in a study want to be able to conclude that watching television
CAUSES poor academic performance and is not merely ASSOCIATED with school
performance they need to…
(a.) Conduct a well-controlled experiment
(b.) Use an unbiased random sample in an observational study
(c.) both (a.) and (b.) would be appropriate studies for the researchers
(d.) neither of these types of studies can be used to establish a cause-and-effect
relationship between watching TV and academic performance
28.
The Physicians’ Health Study tried to find out if taking aspirin regularly helps prevent
heart attacks and/or strokes. The subjects were 20,071 healthy male doctors at least 40
years old. The subjects were randomly divided so that one group took aspirin every other
day and a second group took a placebo. The doctors in the aspirin group had far fewer
heart attacks than those in the control group. This study is an…
(a.) observational study, so it is reasonable to conclude that aspirin reduced risk of heart
of attacks.
(b.) observational study so it is inappropriate to draw cause and effect conclusions
(c.) experiment so it is reasonable to conclude that aspirin reduced risk of heart of attacks.
(d.) experiment so it is inappropriate to draw cause and effect conclusions
29.
What is the role of randomization in an experiment?
(a.) A random sample of subjects is selected from a population to avoid bias
(b.) Subjects are randomly assigned to treatments so create experimental groups that are
similar
(c.) Treatments are applied to every subject at random intervals
(d.) Experimenters must randomly decide what the purpose of the study is
30.
The control group in an experiment should be designed to receive:
(a.) the opposite of the experiences afforded the experimental group.
(b.) the same experiences afforded the experimental group except for the
treatment under examination.
(c.) the experiences afforded the experimental group except for
receiving the treatment at random intervals.
(d.) the experiences which constitute an absence of the experiences
received by the experimental group.
31.
In an experiment to see if Smartfood Popcorn makes people smarter, 50 students are
randomly assigned to two groups. The first group receives Smartfood popcorn and the
second gets regular popcorn. Then each student writes an essay on an assigned topic. The
essays are scored by a teacher and the results are compared for the two groups to see if
Smartfood had a positive effect on essay writing. Which of the following would ensure
blindness and double-blindness in this study?
(a.) the students and reseachers should both wear blindfolds
(b.) no one should know whether Smartfood was used for either group.
(c.) the students should not know whether they got Smartfood or a different brand of
popcorn, and the teacher should not know which group the the student was in while
grading the essay.
(d.) Smartfood should be given to both groups but in random intervals so that the
students do not know when they are getting it
32.
An experiment is said to take into account the principle of blindness if ___________,
and it could be said to be double-blind if _____________.
(a.) the subjects are randomly assigned to treatments;
those evaluating the subjects are blindfolded
(b.) the subjects are not aware of which treatment group they are in;
those evaluating the subjects are not aware of which treatment group the subjects are in
(c.) the subjects are selected at random from the population;
those evaluating the subjects are not aware of which treatment group the subjects are in
(d.) the subjects are not aware of which treatment group they are in;
the two treatment groups are never come in contact
33.
In an experiment studying the effect of a new drug for treating high blood pressure, the
control group in the experiment should receive
(a.) a lower dose of the drug
(b.) nothing
(c.) a placebo
(d.) euthanasia
34.
Consider an experiment to investigate the efficacy of different insecticides in controlling
pests and their effects on subsequent yield. What is the best reason for randomly
assigning treatment levels (spraying or not spraying) to the experimental units (farms)?
(a) Randomization makes the experiment easier to conduct because we can apply the
insecticide in any pattern rather than in a systematic fashion.
(b) Randomization makes the analysis easier because the data can be collected and
entered into the computer in any order.
(c) Randomization is required by statistical consultants before they will help you analyze
the experiment.
(d) Randomization will tend to average out all other uncontrolled variables such as soil
fertility so that they are not confounded with the treatment effects.
35.
Researchers have observed that drinking red wine seems to lead to fewer men having
heart attacks. More recently, others have noted that drinking red wine leads to
headaches and people with headaches tend to take aspirin. Furthermore, aspirin is
known to reduce the changes of having heart attacks. Given these facts, the relationship
between drinking red wine and having heart attacks would be best described as
confounded by the use of aspirin because
(a.) the cause-and-effect relationship between aspirin and reducing the risk of heart
attacks can be inferred from this study while the effect of drinking wine cannot
(b.) aspirin was not a variable measured in the study and was not controlled for in the
study but could affect the response variable
(c.) it may be that heart attacks cause people to drink wine instead of the other way
around
(d.) there is a placebo effect at work in this experiment.
36.
Which of the following is a confounding variable?
(a.) a variable which was not measured but may explain the relationship between the
variables that were measured
(b.) a response variable that may also be thought of as explanatory
(c.) a placebo
(d.) any variable could be considered confoundin
37.
Which is NOT a correct interpretation of the Law of Large Numbers?
38.
(a.)
If you flip a coin 10 times we expect to get 5 “heads” on average
(b.)
If you flip a coin a large number of times you are more likely to get close to 50%
“heads” than if you flip a coin a small number of times.
(c.)
If you flip a coin twice and get “heads” both times, the next flip will most likely
come up “tails”
(d.)
If you flip a coin 50 times, you probably won’t get exactly 25 “heads” but you are
likely to get somewhat close to 50% “heads”
Which of the following is NOT a possible probability?
(a.) 25/100
(b.) 1.25
(c.) 1
(d.) 0
39.
Tina has 5 red, 6 blue, 3 white, and 4 orange marbles. All marbles are put in a sack and
one marble is selected at random. Compute the probability of drawing a red marble and
the probability of drawing a blue or white marble.
(a.) 4/19; 9/20
(b.) 3/10; 11/20
(c.) 5/18; 1/2
(d.) 9/21; 7/18
40.
41.
A die is rolled. If the number rolled is odd, Player A wins $2 from Player B. If it is a 6, A
wins $4 from B. Otherwise B wins $5 from A. Is this a fair game?
(a.)
Yes, because the expected value is 0.
(b.)
Yes, because the expected value is positive for player A
(c.)
No, because the expected value is negative for player A
(d.)
No, because the expected value is 0
When rolling a pair of 6-sided dice, what is the probability of rolling a sum of 7?
(a.) 1/6
(b.) 3/14
(c.) 5/12
(d.) 11/36
42.
Tina has 5 red, 6 blue, 3 white, and 4 orange marbles. All marbles are put in a sack and
one marble is selected at random. Compute the probability of drawing a red marble and
the probability of drawing a blue or white marble.
(a.) 4/19; 9/20
(b.) 3/10; 11/20
(c.) 5/18; 1/2
(d.) 9/21; 7/18
43.
Which is a correct interpretation of the Law of Large Numbers?
(a.) If you flip a coin 10 times and get 9 heads, we expect to get tails on the next toss.
(b.) If you flip a coin a small number of times you are more likely to get close to 50%
“heads” than if you flip a coin a large number of times.
(c.) If you flip a coin twice and get “heads” both times, the next flip will most likely
come up “tails”
(d.) If you flip a coin 50 times, you probably won’t get exactly 25 “heads” but you are
likely to get somewhat close to 50% “heads”
44.
Use StatCrunch to calculate the correlation between position and price.
(a) 39.84
(b) 8.42
(c) .99
(d) .88
45.
Use StatCrunch to calculate the linear regression equation of price versus position.
Which of the following is an appropriate interpretation of the slope of the
regression equation?
(a) Every increase in price of one dollar tends to be associated with an increase in
one position
(b) There is a rise of 39.84 and a run of 8.42
(c) The position is unrelated to the price
(d) An increase in one position tends to go with an increase in price of $8.42
46.
What is the y-intercept?
(a) 39.84
(b) 8.42
(c) .99
(d) .88
47.
If there were a 23rd property, what price would be predicted by the regression
equation for this new property?
(a) $233.52
(b) $15.71
(c) $1912.43
(d) $23.23
48.
Calculate the linear regression of rent versus price. (Note that price is the
explanatory variable and rent is the response.)
(a) price = -3.2 + .2011(rent)
(b) rent = -4.7 + .1055(price)
(c) price = 2.3 + .2110(rent)
(d) rent = 7.4 + .5501(price)
49.
50.
A negative residual value indicates that…
(a.) the average error is greater than the predicted error
(b.) the predicted value is greater than the observed value
(c.) the observed value is greater than the predicted value
(d.) the error in y is explained by x
A certain random event only two possible outcomes, A and B. If the probability
that A happens is .2, then the probability that B happens is
(a) .8
(b) .5
(c) .2
(d) cannot be determined