Download Stat 250

Stat 250.3 – Practice Quiz 2
QUESTIONS 1 TO 4: Decide if the study is an observational study or an experiment.
1. Twenty blue-fin tuna were randomly assigned to two tanks of water, 10 tuna in each tank.
One tank was polluted with methyl mercury, while the other tank was not polluted. The
survival times of the fish in the two tanks were compared.
A. Observational Study
B. Experiment
KEY B
2. A biologist measured the increasing amounts of phosphorus in Lake Erie and observed a
decreasing number of lake trout over a 5-year period.
A. Observational Study
B. Experiment
KEY A
3. Decide if the study was a retrospective or prospective study : A case-control study found
higher exposure to gases, dusts, and fumes in the workplace among patients with bronchitis
(an inflammation of the lungs) than among patients without bronchitis.
A. Retrospective
B. Prospective
KEY A
4. A researcher conducts a study to determine whether or not taking Vitamin C prevents colds.
What is the explanatory variable in this study?
A. Whether or not one takes Vitamin C.
B. Whether or not one gets colds.
C. Whether or not one is a participant in the study.
D. Whether or not one knows which treatment one is taking.
KEY: A
QUESTIONS 5 TO 7: Researchers would like to compare meditation and exercise to see which is
more effective for reducing stress. One hundred people who suffer from high stress volunteer to
participate in a study for ten weeks. Participants will either be given a 10-week course in
meditation or will participate in a 10-week exercise program. The researchers must decide
whether to randomly assign the volunteers to the two programs, or allow them to choose.
5. Which of the following is the main advantage of randomly assigning participants to the two
programs rather than allowing them to choose?
A. The participants are more likely to stick with the program for the full 10 weeks.
B. Confounding variables, such as past practice of meditation, should be approximately
equal for the two groups.
C. Random assignment ensures that the two sample sizes are equal and that requirement
is necessary in studies like this one.
D. Random assignment will allow the results to be extended to the population of all adults.
KEY: B
6. Which of the following is an advantage of allowing participants to choose the program in
which to participate?
A. Allowing them to choose will increase the ecological validity of the study because in the
real world people choose their own programs.
B. Confounding variables, such as past practice of meditation, should be approximately
equal for the two groups.
C. Allowing participants to choose will allow the results to be extended to the population of
all adults.
D. If participants are allowed to choose then a cause and effect conclusion can be made.
Key: A
7. Suppose participants are randomly assigned to the two programs and a psychologist
measures their stress levels before and after the 10-week program, without being told who is
in which program. This experiment would be:
A. Single blind as long as the participants are not told the results of the stress level
measurements.
B. Single blind because the psychologist doesn't know who is in which program, but the
participants do know.
C. Double blind as long as the participants are not told the results of the stress level
measurements.
D. Neither single nor double blind.
KEY: B
8. Research is done to see whether taking oral contraceptives increases women’s blood
pressures. The blood pressures of women who take oral contraceptives are compared to the
blood pressures of women who do not take oral contraceptive. A complicating factor is that
the women who take oral contraceptives tend to be younger than the others. This must be
taken into account because blood pressure increases with age. Which variable is the
response variable in this study?
A. Age
B. Blood pressure
C. Oral contraceptive use
D. Both age and oral contraceptive use are response variables in this study.
KEY: B
9. A tea manufacturer is trying to decide whether to add peach flavoring or mango flavoring to
green tea for a new product. A study is done by stopping customers at a grocery store and
asking them to drink a small cup of tea with each flavoring, then to rate each of the two
flavors on a scale from 1 to 10. The order in which the teas are presented is randomly
assigned for each person. This study is an example of:
A. An observational study.
B. A sample survey.
C. A case-control study.
D. A matched-pairs design.
KEY: D
10. Eighty individuals who wished to lose weight were randomly divided into two groups of 40.
One group was given an exercise program to follow while the other group was given a special
diet. After three months, the researcher compared mean weight losses in the two groups.
What type of study is this?
A. Observational study
B. Case control study
C. Matched pairs study
D. Randomized experiment
KEY: D
Questions 11 to 14: A student wants to watch television. She receives 6 stations, which are
broadcasting separate shows on baseball, football, basketball, local news, national news, and
international news. The student is too tired to check which channels the shows are playing, so
she picks a channel at random.
11. The two events S = [she watches sports] and N = [she watches news] are
A. Independent events
B. Disjoint (mutually exclusive) events
C. Each simple events
D. None of the above
KEY: B
12. The two events F = [she watches football] and S = [she watches sports] are
A. Independent events
B. Disjoint (mutually exclusive) events
C. Each simple events
D. None of the above
KEY: D
13. Two students, Michelle and Charles, who don’t know each other, each choose a channel.
The two events, N = [Charles watches news] and F = [Michelle watches football] are
A. Independent events
B. Disjoint (mutually exclusive) events
C. Each simple events
D. None of the above
KEY: A
14. If one card is randomly picked from a standard deck of 52 cards, the probability that the card
will be a red suit (Heart or Diamond), or a face card (Jack, Queen, or King), or both, is
A. 50.0% (26/52)
B. 61.5% (32/52)
C. 76.9% (40/52)
D. 88.5% (46/52)
KEY: B
15. A card is drawn at random from a standard 52-card deck. The conditional probability that the
card is a King given that a face card (Jack, Queen, or King) was drawn is
A.
20.0% (1/5)
B.
25.0% (1/4)
C. 33.3% (1/3)
D. 50.0% (1/2)
KEY: C
17. When a fair coin is flipped 6 times, the probability of getting an odd number of heads (1, 3, or
5) is 0.500. The probability of getting more than 3 heads is 0.344, and the probability of
getting 5 heads is .094. What is the probability of getting either an odd number of heads or
more than 3 heads?
KEY: 0.75