STAT EXAM 1 ASSIGNMENT REVIEW
QUESTIONS AND ANSWERS WITH
VERIFIED SOLUTIONS 100%
CORRECT
The belief that one is receiving some type of treatment has been demonstrated to
actually affect the outcome of the study, so a placebo is often an important measure of
a study. In this way, theoretically, any difference between the treatment group(s) and
the placebo group can be attributed to the "real" impact from the treatment(s).
It is a desirable characteristic of a study for the sampling frame to be as close in size
and similarity to the sample as possible. - CORRECT ANSWES -- False
It is desirable that the sampling frame be as similar as possible to the POPULATION of
interest. The bigger the difference between the population of interest and the sampling
frame, the greater the uncertainty that the results of the study can be generalized to the
population of interest.
If an association is found between the explanatory variable and response variable in a
randomized experiment, it could be that a confounding variable -- which is related to the
explanatory variable and may actually cause the change in the response variable -- is
responsible. - CORRECT ANSWES -- False
This would be true of an observational study, but with a randomized experiment, the
random assignment of the levels of the explanatory variable "average out" the impact of
any confounding variables.
One benefit of a retrospective observational study is that people do not have to try to
accurately recall information from the past. - CORRECT ANSWES -- False
This is false. This would be true of a PROSPECTIVE observational study.
Does the use of cell phones lead to a higher incidence of brain cancer? People with
brain cancer were matched with people who did not have brain cancer on age, gender,
and living environment. Each participant in the study was asked to answer questions
about previous life experiences and exposures. This is a retrospective, case-control
study. - CORRECT ANSWES -- True
,This is a retrospective study since participants are questioned on past life experiences
and exposures. This is also a case-control study since a control group (the group
without cancer that has all the other attributes of the group with cancer) is compared to
the group with cancer (the case group).
A study wants to determine if taking fish oils can reduce depressive symptoms. A group
of 50 volunteers who suffered from mild depression were randomly divided into two
groups. Each person was given a three-month's supply of capsules. One group was
given capsules that contained fish oils while the other group was given capsules that
look and tasted like fish oils, but actually only contained sugar and inert ingredients.
Neither the participants nor the investigator knew what type of capsule they were taking.
At the end of the month, a psychologist evaluated them to determine if their depressive
symptoms had changed. Therefore, we are comparing the "change in depressive
symptoms" for individuals in two groups. Which of the following applies to this study? -
CORRECT ANSWES -- Multi Answer:
randomized experiment
placebo
double-blind
independent samples
This is a randomized experiment since a variable, "type of capsule," is randomly
assigned. The control group is given a placebo. The study is double-blind since neither
the participants nor the investigator knew which type of capsule each person was
taking. These are independent samples since each person only took one type of pill,
and participants were not paired in any other way. A block design is only used with
dependent samples.
As stated in the article, about what aspects of the Gallup Poll are Americans most
skeptical? - CORRECT ANSWES -- They don't see how the views of 1000 people can
represent those of hundreds of millions. They also wonder how Gallup's results can
differ so much from their own impressions of what people think, how Gallup selects
people for their polls, and why they have never been interviewed.
What have you learned from this lesson or from this article that helps you not share the
same skepticism (see prior question) described in the Gallup Poll article? - CORRECT
ANSWES -- Random sampling works. A random sample and poll of even just 1,000
people can accurately represent the views of millions and has a margin of error of
approximately +/- 3%.
What is probability sampling as defined by the Gallup Poll? - CORRECT ANSWES --
"Probability Sampling" is a sampling method for which there are known probabilities for
each individual in the population to get into the sample. "If selected correctly, a
randomly selected small sample of a population of people can represent the attitudes,
opinions, or projected behavior of all of the people from which the sample is obtained."
, Often households have more than one adult who is a part of Gallup Poll's sampling
frame. How does Gallup randomly select one adult from such households? - CORRECT
ANSWES -- They ask to speak with the adult in the house (age 18+) who has had the
most recent birthday.
Use the information below to answer the questions that follow:
that follow:
A group of children ages 9 to 13 completed an education program related to calcium
intake. Subsequent to the program, their daily calcium intake was measured over a 3-
day period, and the average daily calcium intake (mg) was calculated and plotted
(below). - CORRECT ANSWES -- A group of children ages 9 to 13 completed an
education program related to calcium intake. Subsequent to the program, their daily
calcium intake was measured over a 3-day period, and the average daily calcium intake
(mg) was calculated and plotted (below).
Which of the following most accurately describes the shape of the data summarized in
the histogram above? - CORRECT ANSWES -- Symmetric
The data are quite symmetric. The bulk of the data are in the middle with fairly equal
tails in both directions.
For the calcium intake data, how would you expect the values of the mean and median
to compare? - CORRECT ANSWES -- The mean and median are about the same.
For symmetric data, the mean and median will be similar.
Based on the histogram above, which of the following is most likely to be the value of
the median? - CORRECT ANSWES -- 1100
With symmetric data, the median should be (roughly) in the middle, which would be
approximately 1100.
Based on the histogram above, how many of the children can you be certain had a
average daily calcium intake of less than 800 mg? - CORRECT ANSWES -- 4
Because the second bar includes values both below and above 800 mg, we can only be
CERTAIN that the first bar is entirely below 800 mg. The height of the first bar indicates
that it represents four children.
Which of the following is the approximate 75th percentile of the data? - CORRECT
ANSWES -- 1250
The 75th percentile separates the lower 75% of the data from the upper 25% of the
data. Based on the graph, the only possible value among the options is 1250.
800 falls toward the lower end of the data, so it couldn't possibly be the 75th percentile.
Only a small percentage of the data falls at or below 800.
QUESTIONS AND ANSWERS WITH
VERIFIED SOLUTIONS 100%
CORRECT
The belief that one is receiving some type of treatment has been demonstrated to
actually affect the outcome of the study, so a placebo is often an important measure of
a study. In this way, theoretically, any difference between the treatment group(s) and
the placebo group can be attributed to the "real" impact from the treatment(s).
It is a desirable characteristic of a study for the sampling frame to be as close in size
and similarity to the sample as possible. - CORRECT ANSWES -- False
It is desirable that the sampling frame be as similar as possible to the POPULATION of
interest. The bigger the difference between the population of interest and the sampling
frame, the greater the uncertainty that the results of the study can be generalized to the
population of interest.
If an association is found between the explanatory variable and response variable in a
randomized experiment, it could be that a confounding variable -- which is related to the
explanatory variable and may actually cause the change in the response variable -- is
responsible. - CORRECT ANSWES -- False
This would be true of an observational study, but with a randomized experiment, the
random assignment of the levels of the explanatory variable "average out" the impact of
any confounding variables.
One benefit of a retrospective observational study is that people do not have to try to
accurately recall information from the past. - CORRECT ANSWES -- False
This is false. This would be true of a PROSPECTIVE observational study.
Does the use of cell phones lead to a higher incidence of brain cancer? People with
brain cancer were matched with people who did not have brain cancer on age, gender,
and living environment. Each participant in the study was asked to answer questions
about previous life experiences and exposures. This is a retrospective, case-control
study. - CORRECT ANSWES -- True
,This is a retrospective study since participants are questioned on past life experiences
and exposures. This is also a case-control study since a control group (the group
without cancer that has all the other attributes of the group with cancer) is compared to
the group with cancer (the case group).
A study wants to determine if taking fish oils can reduce depressive symptoms. A group
of 50 volunteers who suffered from mild depression were randomly divided into two
groups. Each person was given a three-month's supply of capsules. One group was
given capsules that contained fish oils while the other group was given capsules that
look and tasted like fish oils, but actually only contained sugar and inert ingredients.
Neither the participants nor the investigator knew what type of capsule they were taking.
At the end of the month, a psychologist evaluated them to determine if their depressive
symptoms had changed. Therefore, we are comparing the "change in depressive
symptoms" for individuals in two groups. Which of the following applies to this study? -
CORRECT ANSWES -- Multi Answer:
randomized experiment
placebo
double-blind
independent samples
This is a randomized experiment since a variable, "type of capsule," is randomly
assigned. The control group is given a placebo. The study is double-blind since neither
the participants nor the investigator knew which type of capsule each person was
taking. These are independent samples since each person only took one type of pill,
and participants were not paired in any other way. A block design is only used with
dependent samples.
As stated in the article, about what aspects of the Gallup Poll are Americans most
skeptical? - CORRECT ANSWES -- They don't see how the views of 1000 people can
represent those of hundreds of millions. They also wonder how Gallup's results can
differ so much from their own impressions of what people think, how Gallup selects
people for their polls, and why they have never been interviewed.
What have you learned from this lesson or from this article that helps you not share the
same skepticism (see prior question) described in the Gallup Poll article? - CORRECT
ANSWES -- Random sampling works. A random sample and poll of even just 1,000
people can accurately represent the views of millions and has a margin of error of
approximately +/- 3%.
What is probability sampling as defined by the Gallup Poll? - CORRECT ANSWES --
"Probability Sampling" is a sampling method for which there are known probabilities for
each individual in the population to get into the sample. "If selected correctly, a
randomly selected small sample of a population of people can represent the attitudes,
opinions, or projected behavior of all of the people from which the sample is obtained."
, Often households have more than one adult who is a part of Gallup Poll's sampling
frame. How does Gallup randomly select one adult from such households? - CORRECT
ANSWES -- They ask to speak with the adult in the house (age 18+) who has had the
most recent birthday.
Use the information below to answer the questions that follow:
that follow:
A group of children ages 9 to 13 completed an education program related to calcium
intake. Subsequent to the program, their daily calcium intake was measured over a 3-
day period, and the average daily calcium intake (mg) was calculated and plotted
(below). - CORRECT ANSWES -- A group of children ages 9 to 13 completed an
education program related to calcium intake. Subsequent to the program, their daily
calcium intake was measured over a 3-day period, and the average daily calcium intake
(mg) was calculated and plotted (below).
Which of the following most accurately describes the shape of the data summarized in
the histogram above? - CORRECT ANSWES -- Symmetric
The data are quite symmetric. The bulk of the data are in the middle with fairly equal
tails in both directions.
For the calcium intake data, how would you expect the values of the mean and median
to compare? - CORRECT ANSWES -- The mean and median are about the same.
For symmetric data, the mean and median will be similar.
Based on the histogram above, which of the following is most likely to be the value of
the median? - CORRECT ANSWES -- 1100
With symmetric data, the median should be (roughly) in the middle, which would be
approximately 1100.
Based on the histogram above, how many of the children can you be certain had a
average daily calcium intake of less than 800 mg? - CORRECT ANSWES -- 4
Because the second bar includes values both below and above 800 mg, we can only be
CERTAIN that the first bar is entirely below 800 mg. The height of the first bar indicates
that it represents four children.
Which of the following is the approximate 75th percentile of the data? - CORRECT
ANSWES -- 1250
The 75th percentile separates the lower 75% of the data from the upper 25% of the
data. Based on the graph, the only possible value among the options is 1250.
800 falls toward the lower end of the data, so it couldn't possibly be the 75th percentile.
Only a small percentage of the data falls at or below 800.
