Stat 411/511
# Quiz 3 Study Guide

Everything that was on Quiz 1 and 2, could also be on Quiz 3.

**Reading:** Sleuth: 3 & 4

**Practice Questions: Conceptual Exercises in Sleuth**

Page 77: 1, 2, 4, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17

Page 106: 1, 2, 3, 4, 6, 7, 8

State the assumptions of the two sample t-test.

To which assumptions, and under what conditions, is the two sample t-test robust?

What does robustness mean?

What does resistance mean?

Give an example of a resistant statistic.

Identify possible sources of dependence in a study design.

Identify data that may benefit from a log-transformation.

Given t-test results on log-transformed data, write a statistical summary on the original scale of measurement.

For the five tests (Wilcoxon Rank Sum, Levene’s Test, Welch’s t-test, Sign Test, Wilcoxon Signed Rank test), you should be able to:

- Say whether the test is used for two independent groups or two paired groups.
- State the null hypothesis for the test.
- State the difference in assumptions relative to the corresponding t-tool (two-sample or paired t-test).
- Say whether the test is resistant to outliers.

For the Wilcoxon Rank Sum test and Sign test you should also be able to:

- State and calculate (on small examples) the test statistic.

Identify appropriate tests from a study description.

Explain why the difference in means doesn’t tell the whole story in the unequal variance case.