Alta Chapter 9 - Hypothesis Testing

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Questions and Answers

What is the formula to find the degrees of freedom?

n - 1

What are the critical values for a two-tailed test with 15 degrees of freedom at a significance level of 0.005?

2.160 and -2.160

3.12

2.947 and -2.947 (correct)

1.697 and -1.697

What is the significance level used by Vae for her hypothesis test?

2.5%

The test statistic for Isabella's hypothesis test is 1.489.

True Signup and view all the answers

In Isabella's test, what conclusion can be drawn based on the test statistic and critical values?

Fail to reject H0 Signup and view all the answers

What is the calculated p-value for a right-tailed test with t = 3.12 and 60 degrees of freedom?

less than 0.005 Signup and view all the answers

Should Rebecca reject or fail to reject the null hypothesis based on her sample data?

Reject Signup and view all the answers

What is the sample mean market value of houses found by Rebecca?

$259,860 Signup and view all the answers

Which of the following results in a null hypothesis p=0.61 and alternative hypothesis p>0.61?

The null hypothesis corresponds to the claim in the study. Signup and view all the answers

What is the test statistic (z-score) of Olivia's one-mean hypothesis test?

3.87 Signup and view all the answers

What is the test statistic (z-score) of Jolyn's hypothesis test?

-0.95 Signup and view all the answers

What is the test statistic (z-score) of the bowler's one-mean hypothesis test?

3.74 Signup and view all the answers

What is the test statistic (z-score) of the baker's one-mean hypothesis test?

12.65 Signup and view all the answers

What is the test statistic (z-score) of William's one-mean hypothesis test?

5.30 Signup and view all the answers

What is the test statistic (z-score) for Floretta's hypothesis test?

Not provided Signup and view all the answers

What is the test statistic for the knee surgery hypothesis test?

-2.90 Signup and view all the answers

What is the test statistic for the unemployment rate hypothesis test?

3.06 Signup and view all the answers

What are the null and alternative hypotheses for Kylie's seed germination test?

H0:p=0.93; Ha:p<0.93 Signup and view all the answers

A t-test is appropriate if the sample size is less than 30.

True Signup and view all the answers

What conclusion did Olivia reach regarding the percentage of tips received by waitstaff?

Do not reject the null hypothesis. Signup and view all the answers

Study Notes

Hypothesis Testing Overview

Null Hypothesis (H0): Represents a statement of no effect or no difference; often reflects a status quo.
Alternative Hypothesis (Ha): Represents what the researcher aims to prove; suggests a difference or effect.
Significance Level (α): Defines the probability of rejecting the null hypothesis when it is true, often set at 0.05 or 0.10.

Hypothesis Testing Procedure

Identify the null and alternative hypotheses.
Determine the significance level (α) for the test.
Collect data to compute the test statistic.
Compare the test statistic against a critical value to decide whether to reject H0.

Test Statistics

Z-Score Calculation:
- Used when population standard deviation is known.
- Formula: ( z = \frac{\bar{x} - \mu_0}{\frac{\sigma}{\sqrt{n}}} )
- Example: Olivia's test yields a z-score of 3.87 when examining golf drive distances.
Sample Mean and Standard Deviation:
- Critical for calculating the test statistic.
- Understanding sample sizes and their impacts on the results (larger samples lead to more reliable estimates).

Common Scenarios

Different Claims:
- A golfer (Olivia) hypothesizes her drive distance is greater than an established average; specific statistical calculations were completed for her case using standard deviation and sample calculations.
Baker's Claim:
- William's hypothesis about bread height's average was tested; obtained a z-score revealing whether to accept or reject his claims based on a threshold.

Example Outcomes

Successful and Unsuccessful Tests:
- Results may lead to rejecting or failing to reject H0 based on whether the calculated test statistics fell within the rejection region defined by the critical values.
- Example of a failed rejection in the context of waitstaff tips indicating that average tips do not differ significantly from established norms.

Special Cases for Proportions

Situations may arise requiring hypothesis testing for proportions, analyzed through different z-scores.
Formulation includes determining sample proportions, successful events, and failure rates.

Selecting the Right Test

T-Tests vs. Z-Tests:
- T-tests are appropriate when the population standard deviation is unknown and the sample size is small.
- Require knowledge of the sample mean, sample size, and sample standard deviation.

Two-Tailed vs. One-Tailed Tests

Understanding when to apply left-tail, right-tail, or two-tailed tests based on the nature of the hypotheses.
Example from a linguist’s study about study time for languages showcases the importance of tail direction.

Conclusions from Testing

Deciding whether to reject or accept the null hypothesis based on calculated p-values and corresponding significance levels plays a critical role in hypothesis testing outcomes.

Key Calculations

Results include detailed calculations for various scenarios such as:
- z-score examples for Olivia (3.87), baker (some higher z-scores) leading to evidence rejection or acceptance of claims.
- Various calculated test statistics rounded to two decimal places for clarity and communication of results.

Summary

Hypothesis testing is a systematic approach to validate claims using statistical evidence, critical for decision-making in research and practical applications across various fields.### Hypothesis Testing Overview
Null hypothesis (H0) posits that the population mean is a specific value (e.g., $250,000 for Rebecca).
Alternative hypothesis (Ha) suggests that the population mean is greater than that specific value.

Conclusion for Card 70

Do not reject null hypothesis due to calculated test statistic and p-value considerations.
Sample mean salary from 61 employees is $56,500 with a standard deviation of $3,750.
Test statistic calculated as 3.12 with 60 degrees of freedom signifies a right-tailed test.
The p-value associated with t = 3.12 is less than 0.005, indicating strong evidence against null hypothesis if true.

Conclusion for Card 74

Rebecca tests whether the mean market value of houses is greater than $250,000.
Sample of 35 houses gives a mean market value of $259,860 with a standard deviation of $24,922.
t-statistic calculated as approximately 2.34 with 34 degrees of freedom.
At a significance level (α) of 0.05, Rebecca should assess whether to reject or fail to reject the null hypothesis based on p-value interpretation, which should be obtained using the t-distribution table.

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Description

Test your understanding of hypothesis testing with this quiz from Alta Chapter 9. Explore null and alternative hypotheses through practical scenarios, enhancing your grasp of statistical concepts. Perfect for mastering key terms related to hypothesis testing.