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Ch. 7 - Hypothesis Testing with One Sample
Larson - Elementary Statistics: Picturing the World 8th Edition
Larson8th EditionElementary Statistics: Picturing the WorldISBN: 9780137493470Not the one you use?Change textbook
Chapter 7, Problem 7.1.51b

Writing Hypotheses: Backpack Manufacturer A backpack manufacturer claims that the mean life of its competitor’s backpacks is less than 5 years. You are asked to perform a hypothesis test to test this claim. How would you write the null and alternative hypotheses when


b. you represent the competitor and want to reject the claim?

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1
Step 1: Understand the context of the problem. The backpack manufacturer claims that the mean life of its competitor’s backpacks is less than 5 years. This is the alternative hypothesis (Hₐ) because it represents the claim being tested.
Step 2: Define the null hypothesis (H₀). The null hypothesis is the opposite of the alternative hypothesis and represents the status quo or no effect. In this case, H₀: μ ≥ 5, where μ is the mean life of the competitor’s backpacks.
Step 3: Define the alternative hypothesis (Hₐ). Since the manufacturer claims the mean life is less than 5 years, the alternative hypothesis is Hₐ: μ < 5.
Step 4: Represent the competitor and aim to reject the claim. To reject the claim, you would test the null hypothesis (H₀: μ ≥ 5) against the alternative hypothesis (Hₐ: μ < 5) using appropriate statistical methods.
Step 5: Choose the significance level (α) and perform the hypothesis test. Commonly, α = 0.05 is used. Based on the test results (e.g., p-value or test statistic), determine whether to reject H₀ or fail to reject H₀.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Null Hypothesis (H0)

The null hypothesis is a statement that indicates no effect or no difference, serving as a default position in hypothesis testing. In this context, it would assert that the mean life of the competitor's backpacks is equal to or greater than 5 years, which is the claim being tested against.
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Step 1: Write Hypotheses

Alternative Hypothesis (H1)

The alternative hypothesis represents the statement that contradicts the null hypothesis, suggesting that there is an effect or a difference. For this scenario, if you want to reject the claim, the alternative hypothesis would state that the mean life of the competitor's backpacks is greater than 5 years.
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Hypothesis Testing

Hypothesis testing is a statistical method used to make inferences about population parameters based on sample data. It involves calculating a test statistic and comparing it to a critical value to determine whether to reject the null hypothesis in favor of the alternative hypothesis, thus providing evidence for or against the claim.
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Related Practice
Textbook Question

Graphical Analysis In Exercises 9–12, state whether each standardized test statistic t allows you to reject the null hypothesis. Explain.


c. t = -2.096


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Textbook Question

Interpreting a Decision In Exercises 43–48, determine whether the claim represents the null hypothesis or the alternative hypothesis. If a hypothesis test is performed, how should you interpret a decision that

         

b. fails to reject the null hypothesis?


Marketing A fitness equipment company claims that its competitor’s home gym does not have a customer satisfaction rate of 99%.

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Textbook Question

Graphical Analysis In Exercises 9–12, state whether each standardized test statistic t allows you to reject the null hypothesis. Explain.


b. t = 0

69
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Textbook Question

Interpreting a Decision In Exercises 43–48, determine whether the claim represents the null hypothesis or the alternative hypothesis. If a hypothesis test is performed, how should you interpret a decision that

         

b. fails to reject the null hypothesis?


Rent A recent study claims that at least 20% of renters are behind on rent payments in New Jersey. 

54
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Textbook Question

Interpreting a Decision In Exercises 43–48, determine whether the claim represents the null hypothesis or the alternative hypothesis. If a hypothesis test is performed, how should you interpret a decision that

         

b. fails to reject the null hypothesis?


Gas Mileage An automotive manufacturer claims that the standard deviation for the gas mileage of one of the vehicles it manufactures is 3.9 miles per gallon.

72
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Textbook Question

Graphical Analysis In Exercises 9–12, state whether each standardized test statistic t allows you to reject the null hypothesis. Explain.


b. t = 1.42


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