PBSI Quizzes Questions With Complete Solutions
The statistics department at Cal Poly, San Luis Obispo, has 18
faculty members and 80 undergraduate majors. Use Table A,
starting at line 111, to choose a stratified sample of 1 faculty
member and 1 student to attend a reception being held by the
university president.
Begin numbering students and faculty with 01. Select the
number corresponding to the student chosen. (You already
chose the faculty member in the previous question.)
Line 111: 81486 69487 60513 09297 00412 71238 27649 39950
48
A statistics class has 10 graduate students and 40 undergraduate
students. You want to randomly sample 10% of the students in
the class. One graduate student and four undergraduate students
are selected at random.
Which of the following is not correct?
Because each student has a 10% chance of being selected, this is
a simple random sample.
- Because each sample includes exactly one graduate student
and four undergraduate students, this is not a random sample.
Does coaching raise SAT scores? Because many students score
higher on a second try, even without coaching, a study looked at
a simple random sample of 4200 students who took the SAT
twice. Of these, 500 had taken coaching courses between their
,two attempts at the SAT. The study compared the average
increase in scores (out of the total possible score of 2400) for
students who were coached with the average increase for
students who were not coached.
The study is 95% confident that the difference between average
scores for coached and uncoached students is between 28 and 57
points. To be 99% confident, the range of points would be:
wider because higher confidence requires a larger margin of
error.
Suppose a forester wants to estimate of the average size of the
trees in her local park. She already has a data set that contains
the unique identification number, species identity, and location
for each of the 10,000 trees in the park. She decides to estimate
the trunk diameter of the population from a sample of trees.
Select the sampling method that would be used for the following
description.
She sorts the data set by tree identification code. She uses a
random number generator to select the first tree to measure. She
then selects every 30th tree in the data set until her sample
contains 50 trees.
systematic
Does St. John's wort have a significant effect in treating major
depression? A study looked at 340 adult outpatients suffering
from major depression as measured by their HAM-D score,
randomly assigning each subject to either a placebo, St. John's
wort, or a second active treatment for comparison.
, The study found the difference in treating major depression as
measured by improvement in HAM-D scores between St. John's
wort and the placebo was not statistically significant. This
means that:
a difference this big could easily occur just by chance even if St.
John's wort does no better than the placebo.
(From the news) On September 1, 2018, The Columbus
Dispatch reported on a study about political polarization and
social media. In this study, 901 Democrats and 751 Republicans
were recruited. The Democrats were randomly divided into two
groups. All were asked to follow an automated Twitter account
(Twitter bot) each day for one month. One group received
tweets with a liberal point-of-view, and the other tweets with a
conservative point-of-view. Likewise, Republicans were
randomly divided into two groups and received the same two
treatments (liberal or conservative tweets). All subjects were
given a test, both before and after the experiment that scored
them on a liberal/conservative scale. Changes in scores were the
response variable.
Is the political affiliation of the subjects (Democrat or
Republican) a treatment variable or a block? Why?
Political affiliation is a block because participants were split on
this factor initially before seeing the tweets.
(From the news) On September 1, 2018, The Columbus
Dispatch reported on a study about political polarization and
The statistics department at Cal Poly, San Luis Obispo, has 18
faculty members and 80 undergraduate majors. Use Table A,
starting at line 111, to choose a stratified sample of 1 faculty
member and 1 student to attend a reception being held by the
university president.
Begin numbering students and faculty with 01. Select the
number corresponding to the student chosen. (You already
chose the faculty member in the previous question.)
Line 111: 81486 69487 60513 09297 00412 71238 27649 39950
48
A statistics class has 10 graduate students and 40 undergraduate
students. You want to randomly sample 10% of the students in
the class. One graduate student and four undergraduate students
are selected at random.
Which of the following is not correct?
Because each student has a 10% chance of being selected, this is
a simple random sample.
- Because each sample includes exactly one graduate student
and four undergraduate students, this is not a random sample.
Does coaching raise SAT scores? Because many students score
higher on a second try, even without coaching, a study looked at
a simple random sample of 4200 students who took the SAT
twice. Of these, 500 had taken coaching courses between their
,two attempts at the SAT. The study compared the average
increase in scores (out of the total possible score of 2400) for
students who were coached with the average increase for
students who were not coached.
The study is 95% confident that the difference between average
scores for coached and uncoached students is between 28 and 57
points. To be 99% confident, the range of points would be:
wider because higher confidence requires a larger margin of
error.
Suppose a forester wants to estimate of the average size of the
trees in her local park. She already has a data set that contains
the unique identification number, species identity, and location
for each of the 10,000 trees in the park. She decides to estimate
the trunk diameter of the population from a sample of trees.
Select the sampling method that would be used for the following
description.
She sorts the data set by tree identification code. She uses a
random number generator to select the first tree to measure. She
then selects every 30th tree in the data set until her sample
contains 50 trees.
systematic
Does St. John's wort have a significant effect in treating major
depression? A study looked at 340 adult outpatients suffering
from major depression as measured by their HAM-D score,
randomly assigning each subject to either a placebo, St. John's
wort, or a second active treatment for comparison.
, The study found the difference in treating major depression as
measured by improvement in HAM-D scores between St. John's
wort and the placebo was not statistically significant. This
means that:
a difference this big could easily occur just by chance even if St.
John's wort does no better than the placebo.
(From the news) On September 1, 2018, The Columbus
Dispatch reported on a study about political polarization and
social media. In this study, 901 Democrats and 751 Republicans
were recruited. The Democrats were randomly divided into two
groups. All were asked to follow an automated Twitter account
(Twitter bot) each day for one month. One group received
tweets with a liberal point-of-view, and the other tweets with a
conservative point-of-view. Likewise, Republicans were
randomly divided into two groups and received the same two
treatments (liberal or conservative tweets). All subjects were
given a test, both before and after the experiment that scored
them on a liberal/conservative scale. Changes in scores were the
response variable.
Is the political affiliation of the subjects (Democrat or
Republican) a treatment variable or a block? Why?
Political affiliation is a block because participants were split on
this factor initially before seeing the tweets.
(From the news) On September 1, 2018, The Columbus
Dispatch reported on a study about political polarization and
