Introductory Statistics
1st Edition
ISBN: 9781938168208
Author: Barbara Illowsky, Susan Dean
Publisher: OpenStax College
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Textbook Question
Chapter 10, Problem 10.2TI
A study is done to determine if Company A retains its workers longer than Company B. Company A samples 15workers, and their average time with the company is five years with a standard deviation of 1.2. Company B samples 20 workers, and their average time with the company is 4.5 years with a standard deviation of 0.8. The populations are
a. Are the population standard deviations known?
b. Conduct an appropriate hypothesis test. At the 5% significance level, what is your conclusion?
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very time you conduct a hypothesis test, there are four possible outcomes of your decision to reject or not reject the null hypothesis: (1) You don’t reject the null hypothesis when it is true, (2) you reject the null hypothesis when it is true, (3) you don’t reject the null hypothesis when it is false, and (4) you reject the null hypothesis when it is false.
Consider the following analogy: You are an airport security screener. For every passenger who passes through your security checkpoint, you must decide whether to select the passenger for further screening based on your assessment of whether he or she is carrying a weapon. Suppose your null hypothesis is that the passenger has a weapon. As in hypothesis testing, there are four possible outcomes of your decision: (1) You select the passenger for further inspection when the passenger has a weapon, (2) you allow the passenger to board her flight when the passenger has a weapon, (3) you select the passenger for further inspection when…
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Ch 6 Sec 4 Homework
Question 4 of 4 (1 point) | Question Attempt: 2 of Unlimited
✓ 2
✓ 3
= 4
Stress at work: In a poll conducted by the General Social Survey, 81% of respondents said that their jobs were sometimes or always stressful. Two hundred
workers are chosen at random. Use the TI-84 Plus calculator as needed. Round your answer to at least four decimal places.
(a) Approximate the probability that 155 or fewer workers find their jobs stressful.
(b) Approximate the probability that more than 145 workers find their jobs stressful.
(c) Approximate the probability that the number of workers who find their jobs stressful is between 154 and 172 inclusive.
Part 1 of 3
The probability that 155 or fewer workers find their jobs stressful is 0.1207
Part 2 of 3
bility that more than 145 workers find their jobs…
A case-control (or retrospective) study was conducted to investigate a relationship between the colors of helmets worn by motorcycle drivers and whether they are injured or killed in a crash. Results are given in the accompanying table. Using a 0.01
significance level, test the claim that injuries are independent of helmet color.
Color of Helmet
Black
White
Yellow
Red
Blue
Controls (not injured)
499
373
32
159
79
Cases (injured
221
108
8
66
38
or killed)
Click here to view the chi-square distribution table.
Chi-square distribution table
Area to the Right of the Critical Value
Degrees of
Freedom
0.995
0.99
0.975
0.95
0.90
0.10
0.05
0.025
0.01
0.005
C. Ho: Injuries and neimet color are dependent
H₁: Injuries and helmet color are independent
D. Ho: Whether a crash occurs and helmet color are dependent
1
0.001
0.004
0.016
2.706
3.841
5.024
6.635
7.879
2
0.010
0.020
0.051
0.103
0.211
4.605
5.991
7.378
9.210
10.597
3
0.072
0.115
0.216
0.352
0.584
6.251
7.815
9.348
11.345
12.838
4
0.207
0.297…
Chapter 10 Solutions
Introductory Statistics
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Ch. 10 - Two Population Means with Unknown Standard...Ch. 10 - Two Population Means with Unknown Standard...Ch. 10 - Two Population Means with Unknown Standard...Ch. 10 - Two Population Means with Unknown Standard...Ch. 10 - Two Population Means with Unknown Standard...Ch. 10 - Two Population Means with Unknown Standard...Ch. 10 - Two Population Means with Unknown Standard...Ch. 10 - Two Population Means with Unknown Standard...Ch. 10 - Two Population Means with Unknown Standard...Ch. 10 - Two Population Means with Unknown Standard...Ch. 10 - Two Population Means with Unknown Standard...Ch. 10 - Two Population Means with Unknown Standard...Ch. 10 - Two Population Means with Unknown Standard...Ch. 10 - Two Population Means with Unknown Standard...Ch. 10 - Use the following information to answer the next...Ch. 10 - Use the following information to answer the next...Ch. 10 - Use the following information to answer the next...Ch. 10 - Use the following information to answer the next...Ch. 10 - 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Researchers interviewed street prostitutes in...Ch. 10 - A powder diet is tested on 49 people, and a liquid...Ch. 10 - Suppose a statistics instructor believes that...Ch. 10 - A study is done to determine if students in the...Ch. 10 - Parents of teenage boys often complain that auto...Ch. 10 - A group of transfer bound students wondered if...Ch. 10 - Some manufacturers claim that non-hybrid sedan...Ch. 10 - A baseball fan wanted to know if there is a...Ch. 10 - One of the questions in a study of marital...Ch. 10 - A recent drug survey showed an increase in the use...Ch. 10 - We are interested in whether the proportions of...Ch. 10 - Elizabeth Mjelde, an art history professor, was...Ch. 10 - A recent year was randomly picked from 1985 to the...Ch. 10 - Use the following information to answer the next...Ch. 10 - Use the following information to answer the next...Ch. 10 - Use the following information to answer the next...Ch. 10 - Researchers conducted a study to find out if there...Ch. 10 - 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