2023W2 - Assignment 8_ COMM 191 201 202 2023W2 Application of Statistics in Business
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University of British Columbia *
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Course
191
Subject
Communications
Date
Apr 3, 2024
Type
Pages
8
Uploaded by CorporalJellyfishMaster1054
3/15/24, 7:44 PM
2023W2 - Assignment 8: COMM 191 201 202 2023W2 Application of Statistics in Business
https://canvas.ubc.ca/courses/129798/quizzes/676553
1/8
2023W2 - Assignment 8
Due Mar 13 at 11:59p.m.
Points 50
Questions 15
Available Mar 6 at 7a.m. - Mar 13 at 11:59p.m.
Time Limit None
This quiz was locked Mar 13 at 11:59p.m..
Attempt History
Attempt
Time
Score
LATEST
Attempt 1
3,344 minutes
46 out of 50
Score for this quiz: 46 out of 50
Submitted Mar 12 at 8:05p.m.
This attempt took 3,344 minutes.
Question 1
4 / 4 pts
Correct!
The distribution is not Normal. It is skewed to the right and has outliers.
Data spreadsheet for Assignment 8
Assignment_8_Datasets_2023W2.xlsx (https://canvas.ubc.ca/courses/129798/files/30060864?
wrap=1) (https://canvas.ubc.ca/courses/129798/files/30060864/download?download_frd=1)
We have all had experiences with calls to technical support telephone centres. One measure of
customer satisfaction is the speed with which questions are answered and problems are resolved.
You are provided with the lengths of telephone technical support calls (times, in minutes) from a random
sample of 50 recent calls to the support line. The data are in the Excel file
Assignment_8_Datasets_2023W2.xlsx
(https://canvas.ubc.ca/courses/129798/files/30060864?wrap=1)
(https://canvas.ubc.ca/courses/129798/files/30060864/download?download_frd=1) (the worksheet is
called TechSupport).
Create a histogram of the sample data (but do not submit it with this assignment). What can we say
about the distribution?
(Select the best answer)
3/15/24, 7:44 PM
2023W2 - Assignment 8: COMM 191 201 202 2023W2 Application of Statistics in Business
https://canvas.ubc.ca/courses/129798/quizzes/676553
2/8
The distribution is not Normal. It is skewed to the left and has outliers.
The distribution is approximately Normal because the sample size is large enough for the Central Limit Theorem to
apply.
The distribution is uniform, as is consistent with research on call centres.
Question 2
3 / 3 pts
The distribution is not Normal. It is skewed to the right and has outliers.
The distribution is not Normal. It is skewed to the left and has outliers.
Correct!
The distribution is approximately Normal because the sample size is large enough for the Central Limit Theorem to
apply.
The distribution is uniform, as is consistent with research on call centres.
Question 3
3 / 3 pts
Correct!
41.52
41.52 (with margin: 0)
Between 41.5 and 41.6
Question 4
0 / 3 pts
What can we say about the sampling distribution of the mean response time?
(Select the best answer)
We wish to know the mean length of all tech support calls. Construct a 95% confidence interval for this
population mean. You will report it in the form: point estimate ± margin of error. The point estimate is:
(Report your answer to two decimal places.)
Continuing from the previous question, for the confidence interval, give the margin of error?
(Report your answer to two decimal places.)
3/15/24, 7:44 PM
2023W2 - Assignment 8: COMM 191 201 202 2023W2 Application of Statistics in Business
https://canvas.ubc.ca/courses/129798/quizzes/676553
3/8
You Answered
8.76
8.98 (with margin: 0)
Between 8.97 and 8.99
Question 5
3 / 3 pts
Correct!
We are 95% confident the interval will contain the true mean call length.
The interval will contain the call lengths of approximately 95% of similar tech support calls.
We are 95% confident that the interval will contain the sampling distribution of the mean call length.
The interval will contain 95% of the standard deviation of call lengths.
Question 6
3 / 3 pts
Answer 1:
Correct!
μ
x
=
≠
<
>
29
30
Thinking about the interpretation of this 95% confidence interval, which of the following is/are correct?
(Select all correct answers)
The tech support supervisor claims that the mean length of tech support calls is 30 minutes. At the 5%
significance level, is there evidence that the claim is not true (i.e. that the mean number of minutes is
different from 30)?
Hypotheses:
H : μ = 30
H : μ ≠ 30
0
A
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3/15/24, 7:44 PM
2023W2 - Assignment 8: COMM 191 201 202 2023W2 Application of Statistics in Business
https://canvas.ubc.ca/courses/129798/quizzes/676553
4/8
50
Answer 2:
μ
x
=
≠
<
>
29
Correct!
30
50
Answer 3:
Correct!
μ
x
=
≠
<
>
29
30
50
Answer 4:
μ
x
=
Correct!
≠
<
>
29
30
50
Answer 5:
μ
3/15/24, 7:44 PM
2023W2 - Assignment 8: COMM 191 201 202 2023W2 Application of Statistics in Business
https://canvas.ubc.ca/courses/129798/quizzes/676553
5/8
x
=
≠
<
>
29
Correct!
30
50
Question 7
4 / 4 pts
Correct!
2.578
2.578 (with margin: 0)
2.5775 (with margin: 0)
Between 2.57 and 2.58
Question 8
3 / 3 pts
Correct!
0.013
0.013 (with margin: 0)
Between 0.012 and 0.014
Question 9
3 / 3 pts
For Questions 7 and 8, carry out the hypothesis test for the supervisor's claim.
What is the test statistic?
(Report your answer to three decimal places.)
Continuing from the previous question, the P-value is:
(Report your answer to three decimal places. This means you should use Excel to get the P-value rather
than the T table on p. A-34.)
3/15/24, 7:44 PM
2023W2 - Assignment 8: COMM 191 201 202 2023W2 Application of Statistics in Business
https://canvas.ubc.ca/courses/129798/quizzes/676553
6/8
Correct!
There is sufficient evidence that the mean call length for the population of tech support calls is different from the
supervisor's claim of 30 minutes.
There is not sufficient evidence that the mean call length for the population of tech support calls is different from the
supervisor's claim of 30 minutes.
There is sufficient evidence that the mean call length for the population of tech support calls is not different from the
supervisor's claim of 30 minutes.
There is not sufficient evidence that the mean call length for the population of tech support calls is not different from the
supervisor's claim of 30 minutes.
Question 10
3 / 3 pts
Correct!
Yes, 30 is outside the confidence interval. It is to the left of the left endpoint.
Yes, 30 is outside the confidence interval. It is to the right of the right endpoint.
Yes, 30 is inside the confidence interval.
Yes, 30 is significantly hypothesizable with 95% confidence.
Question 11
3 / 3 pts
Correct!
What is the most appropriate conclusion to this hypothesis test?
(Select the best answer)
Does the 95% confidence interval you calculated above support the conclusion of your hypothesis test?
(Select the best answer)
Continuing from the previous questions, the tech supervisor thinks that the 3 longest calls shouldn't be
included because they dealt with unusual situations. Redo the hypothesis test with the 3 longest calls
excluded. Answers will be entered in Questions 11, 12 and 13.
First, give the degrees of freedom.
(Report the degrees of freedom as an integer.)
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3/15/24, 7:44 PM
2023W2 - Assignment 8: COMM 191 201 202 2023W2 Application of Statistics in Business
https://canvas.ubc.ca/courses/129798/quizzes/676553
7/8
46
Correct Answers
46
Question 12
4 / 4 pts
Correct!
1.768
1.767 (with margin: 0)
Between 1.76 and 1.77
Question 13
3 / 3 pts
Correct!
0.084
0.084 (with margin: 0)
0.083 (with margin: 0)
Between 0.083 and 0.084
Question 14
3 / 3 pts
Correct!
Yes. The 3 longest calls have a large effect so they should be treated as outliers and excluded.
No. The 3 longest calls do not have any real effect on the result.
No. It is not appropriate to exclude these 3 calls and change conclusions.
Continuing with Question 11, what is the test statistic?
(Report your answer to three decimal places.)
Continuing with Question 11, what is the P-value?
(Report your answer to three decimal places.)
Does the conclusion change with these 3 calls excluded?
(Select the best answer)
3/15/24, 7:44 PM
2023W2 - Assignment 8: COMM 191 201 202 2023W2 Application of Statistics in Business
https://canvas.ubc.ca/courses/129798/quizzes/676553
8/8
Can’t decide. It depends on what happens if, to be fair, the 3 smallest calls are also excluded.
Question 15
4 / 5 pts
Answer 1:
True
Correct!
False
Answer 2:
True
Correct!
False
Answer 3:
You Answered
True
Correct Answer
False
Answer 4:
True
Correct!
False
Answer 5:
Correct!
True
False
Quiz Score: 46 out of 50
Interpreting Confidence Intervals:
A company surveys employees to estimate the costs of lunch in their cafeteria. A 95% confidence
interval for the mean amount of money spent for lunch over a period of six months is ($780,$920). For
each of the following statements, decide whether it is True or False.
95% of all employees pay between $780 and $920 for lunch. False
95% of the sampled employees paid between $780 and $920 for lunch. False
We're 95% confident that employees in this sample average between $780 and $920 for lunch. True
95% of all samples of employees will have average lunch costs between $780 and $920. False
We're 95% confident that the average amount all employees pay for lunch is between $780 and
$920. True