Test for Homogeneity Quiz
The question sheet
Reveal any answer as you study-
Which test decides whether two populations follow the same unknown distribution?
- Goodness-of-fit test
- Test for homogeneity
- Test of independence
- Correlation test
Reveal answer
Answer: Test for homogeneity
Source evidence
PDF page 612: The goodness-of-fit test can be used to decide whether a population fits a given distribution, but it will not suffice to decide whether two populations follow the same unknown distribution. A different test, called the test for homogeneity, can be used to draw a conclusion about whether two populations have the same distribution. To calculate
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The goodness-of-fit test is NOT sufficient to decide whether:
- Two populations follow same distribution
- Data are categorical
- A population fits a distribution
- Expected values are large
Reveal answer
Answer: Two populations follow same distribution
Source evidence
PDF page 612: The goodness-of-fit test can be used to decide whether a population fits a given distribution, but it will not suffice to decide whether two populations follow the same unknown distribution. A different test, called the test for homogeneity, can be used to draw a conclusion about whether two populations have the same distribution. To calculate
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To calculate the test statistic for homogeneity, you follow the same procedure as the:
- Test of independence
- Goodness-of-fit test
- ANOVA test
- Correlation test
Reveal answer
Answer: Test of independence
Source evidence
PDF page 613: the test statistic for a test for homogeneity, follow the same procedure as with the test of independence.
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The alternative hypothesis for a test for homogeneity states the distributions are:
- Normal
- Independent
- Equal
- Not the same
Reveal answer
Answer: Not the same
Source evidence
PDF page 613: Ha: The distributions of the two populations are not the same. Test Statistic Use a test statistic. It is computed in the same way as the test for independence. Degrees of freedom (df) df = (number of columns – 1)(number of rows – 1) Requirements All values in the table must be greater than or equal to five. Common Uses Comparing two populations. For example: men vs. women, before vs. after, east vs. west. The variable is categorical with more than two possible response values.
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Degrees of freedom for a test for homogeneity equal:
- (columns – 1)(rows – 1)
- columns + rows – 2
- number of cells – 1
- rows × columns
Reveal answer
Answer: (columns – 1)(rows – 1)
Source evidence
PDF page 613: Ha: The distributions of the two populations are not the same. Test Statistic Use a test statistic. It is computed in the same way as the test for independence. Degrees of freedom (df) df = (number of columns – 1)(number of rows – 1) Requirements All values in the table must be greater than or equal to five. Common Uses Comparing two populations. For example: men vs. women, before vs. after, east vs. west. The variable is categorical with more than two possible response values.
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In the living arrangements example, the degrees of freedom equaled:
- 3
- 6
- 2
- 4
Reveal answer
Answer: 3
Source evidence
PDF page 613: df = (number of columns – 1)(number of rows – 1) = (4 – 1)(2– 1) = 3
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In the living arrangements example, the test statistic χ² was:
- 0.0175
- 3.2603
- 10.1287
- 0.1959
Reveal answer
Answer: 10.1287
Source evidence
PDF page 613: 2 Calculate the test statistic: χ = 10.1287 (calculator or computer)
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In the living arrangements example, the p-value was:
- 0.05
- 10.1287
- 0.1959
- 0.0175
Reveal answer
Answer: 0.0175
Source evidence
PDF page 613: Probability statement: p-value = P(χ >10.1287) = 0.0175
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The living arrangements conclusion was that the distributions are:
- Independent
- Normal
- The same
- Not the same
Reveal answer
Answer: Not the same
Source evidence
PDF page 615: Conclusion: At a 5 percent level of significance, from the data, there is sufficient evidence to conclude that the distributions of living arrangements for male and female college students are not the same.
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According to the text, the homogeneity test can tell us the distributions differ but not:
- How they differ
- The test statistic
- The p-value
- The df
Reveal answer
Answer: How they differ
Source evidence
PDF page 615: Notice that the conclusion is only that the distributions are not the same. We cannot use the test for homogeneity to draw any conclusions about how they differ.
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In the voter preferences example, the degrees of freedom equaled:
- 4
- 2
- 3
- 1
Reveal answer
Answer: 2
Source evidence
PDF page 616: df = (number of columns – 1)(number of rows – 1) = (3 – 1)(2 – 1) = 2
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In the voter preferences example, the test statistic χ² was:
- 0.0175
- 3.2603
- 10.1287
- 0.1959
Reveal answer
Answer: 3.2603
Source evidence
PDF page 616: 2 Calculate the test statistic: χ = 3.2603 (calculator or computer)
Statistics
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