STAT 217 Unit 1-4 Study Review ACTUAL UPDATED Questions and CORRECT
Answers
C
Terms in this set (229)
b) false Random sampling is a more important consideration than random assignment if
the research question is whether students tend to receive higher scores on essays
if they are encouraged to submit a draft than if they are not so encouraged.
a) true
b) false
a) true Random sampling is a more important consideration than random assignment if
the research question is whether faculty tend to drive older cars than students
drive on your campus.
a) true
b) false
the explanatory and the response variable A randomized experiment allows for the possibility of drawing a cause-and-effect
conclusion between _________ and _.
Randomly assigning the observational units to different Which of the following must happen in a study to allow us to determine cause and
treatment groups effect?
,a) true One of the authors came across an article (USA Today, 2008) that said that on
average Americans have visited 16 states in the United States. Recall that in the
author's sample of 50 students the average number of states the students had
visited was 9.48 and the standard deviation was 7.13. The data are not strongly
skewed. The 95% confidence interval for the average number of states all students
at the author's school have visited is (7.4537, 11.5063).
Judge the validity of the following statement:
The 95% confidence interval that you calculated provides evidence that the
average number of states all students at the author's school have visited is
different from 16.
a) True
b) False
b) Correct An instructor selected a random sample of students in her school and asked them
how many hours per week they expected to spend studying for their courses
outside of class. The sample average was 7.00 hours and the sample standard
deviation was 4.19 hours. The data were not strongly skewed. The theory-based
95% confidence interval for the parameter of interest was 5.6030 and 8.3970.
Judge the correctness of the following interpretation:
We are 95% confident that the average hours/week all students in this school will
spend studying is between 5.6030 and 8.3970.
a) Not correct
b) Correct
d) The new interval would be narrower than (2.619, 3.401) According to a 2011 report by the United States Department of Labor, civilian
hours, because the sample size is bigger. Americans spend 2.75 hours per day watching television. A faculty researcher, Dr.
Sameer, at California Polytechnic State University (Cal Poly) conducts a study to
see whether a different average applies to Cal Poly students. Suppose that for a
random sample of 100 Cal Poly students, the mean and standard deviation of
hours per day spent watching TV turns out to be 3.01 and 1.97 hours, respectively.
The data were used to find a 95% confidence interval: (2.619, 3.401) hours/day.
Suppose that the data had actually been collected from a sample of 150 students,
and not 100, but everything else (mean and SD) was the same as reported earlier.
How, if at all, would the new 95% confidence interval based on these data differ
from the interval mentioned earlier: (2.619, 3.401) hours?
a) More information is needed to answer this question.
b) The new interval would be wider than (2.619, 3.401) hours, because the sample
size is bigger.
c) The new interval would still be (2.619, 3.401) hours, because we are still 95%
confident.
d) The new interval would be narrower than (2.619, 3.401) hours, because the
sample size is bigger.
, a) Manny's; a small sample size will result in more To estimate the proportion of city voters who will vote for the Republican
variability and hence a wider interval. candidate in the election, two students, Manny and Nina, each decide to conduct
polls in the city. Manny selects a random sample of 50 voters, while Nina selects a
random sample of 100 voters. Suppose both samples result in 48% of the voters
saying they will vote for the Republican candidate. Whose 95% confidence
interval will have the larger margin of error: Manny's or Nina's? How are you
deciding?
a) Manny's; a small sample size will result in more variability and hence a wider
interval.
b) Nina's; a large sample size will result in more variability and hence a wider
interval.
c) Neither; the sample size does not affect the margin of error.
a) True A 2SD 95% confidence interval for the probability the competent-face method will
work was calculated to be 0.72 ± 2(0.09) . Based on your confidence interval, we
can conclude that the probability the competent-face method will work is greater
than 50%.
a) True
b) False
b) False If you are concerned that the validity conditions aren't met, use a theory-based
approach to compute a confidence interval for the mean.
a) True
b) False
c) The sample proportion Suppose a 95% confidence interval for a population proportion is found using the
2SD or theory-based method. Which of the following will definitely be contained
in that interval?
a) The p-value
b) The population proportion
c) The sample proportion
c. (0.60, 0.66) d. (0.47, 0.53) A recent Gallup poll showed the president's approval rating at 60%. Some friends
use this information (along with the sample size from the poll) and find theory-
based confidence intervals for the proportion of all adult Americans that approve
of the presidents approve of the president's performance. Of the following four
confidence intervals, identify the ones that were definitely done incorrectly.
(There may be more than term-12one interval that is incorrect.)
a. (0.57, 0.63)
b. (0.58, 0.62)
c. (0.60, 0.66)
d. (0.47, 0.53)
Answers
C
Terms in this set (229)
b) false Random sampling is a more important consideration than random assignment if
the research question is whether students tend to receive higher scores on essays
if they are encouraged to submit a draft than if they are not so encouraged.
a) true
b) false
a) true Random sampling is a more important consideration than random assignment if
the research question is whether faculty tend to drive older cars than students
drive on your campus.
a) true
b) false
the explanatory and the response variable A randomized experiment allows for the possibility of drawing a cause-and-effect
conclusion between _________ and _.
Randomly assigning the observational units to different Which of the following must happen in a study to allow us to determine cause and
treatment groups effect?
,a) true One of the authors came across an article (USA Today, 2008) that said that on
average Americans have visited 16 states in the United States. Recall that in the
author's sample of 50 students the average number of states the students had
visited was 9.48 and the standard deviation was 7.13. The data are not strongly
skewed. The 95% confidence interval for the average number of states all students
at the author's school have visited is (7.4537, 11.5063).
Judge the validity of the following statement:
The 95% confidence interval that you calculated provides evidence that the
average number of states all students at the author's school have visited is
different from 16.
a) True
b) False
b) Correct An instructor selected a random sample of students in her school and asked them
how many hours per week they expected to spend studying for their courses
outside of class. The sample average was 7.00 hours and the sample standard
deviation was 4.19 hours. The data were not strongly skewed. The theory-based
95% confidence interval for the parameter of interest was 5.6030 and 8.3970.
Judge the correctness of the following interpretation:
We are 95% confident that the average hours/week all students in this school will
spend studying is between 5.6030 and 8.3970.
a) Not correct
b) Correct
d) The new interval would be narrower than (2.619, 3.401) According to a 2011 report by the United States Department of Labor, civilian
hours, because the sample size is bigger. Americans spend 2.75 hours per day watching television. A faculty researcher, Dr.
Sameer, at California Polytechnic State University (Cal Poly) conducts a study to
see whether a different average applies to Cal Poly students. Suppose that for a
random sample of 100 Cal Poly students, the mean and standard deviation of
hours per day spent watching TV turns out to be 3.01 and 1.97 hours, respectively.
The data were used to find a 95% confidence interval: (2.619, 3.401) hours/day.
Suppose that the data had actually been collected from a sample of 150 students,
and not 100, but everything else (mean and SD) was the same as reported earlier.
How, if at all, would the new 95% confidence interval based on these data differ
from the interval mentioned earlier: (2.619, 3.401) hours?
a) More information is needed to answer this question.
b) The new interval would be wider than (2.619, 3.401) hours, because the sample
size is bigger.
c) The new interval would still be (2.619, 3.401) hours, because we are still 95%
confident.
d) The new interval would be narrower than (2.619, 3.401) hours, because the
sample size is bigger.
, a) Manny's; a small sample size will result in more To estimate the proportion of city voters who will vote for the Republican
variability and hence a wider interval. candidate in the election, two students, Manny and Nina, each decide to conduct
polls in the city. Manny selects a random sample of 50 voters, while Nina selects a
random sample of 100 voters. Suppose both samples result in 48% of the voters
saying they will vote for the Republican candidate. Whose 95% confidence
interval will have the larger margin of error: Manny's or Nina's? How are you
deciding?
a) Manny's; a small sample size will result in more variability and hence a wider
interval.
b) Nina's; a large sample size will result in more variability and hence a wider
interval.
c) Neither; the sample size does not affect the margin of error.
a) True A 2SD 95% confidence interval for the probability the competent-face method will
work was calculated to be 0.72 ± 2(0.09) . Based on your confidence interval, we
can conclude that the probability the competent-face method will work is greater
than 50%.
a) True
b) False
b) False If you are concerned that the validity conditions aren't met, use a theory-based
approach to compute a confidence interval for the mean.
a) True
b) False
c) The sample proportion Suppose a 95% confidence interval for a population proportion is found using the
2SD or theory-based method. Which of the following will definitely be contained
in that interval?
a) The p-value
b) The population proportion
c) The sample proportion
c. (0.60, 0.66) d. (0.47, 0.53) A recent Gallup poll showed the president's approval rating at 60%. Some friends
use this information (along with the sample size from the poll) and find theory-
based confidence intervals for the proportion of all adult Americans that approve
of the presidents approve of the president's performance. Of the following four
confidence intervals, identify the ones that were definitely done incorrectly.
(There may be more than term-12one interval that is incorrect.)
a. (0.57, 0.63)
b. (0.58, 0.62)
c. (0.60, 0.66)
d. (0.47, 0.53)
