This quiz tests your understanding of hypothesis tests.
Time: 20 minutes. Open book, open notes.
1. A simple random sample of soils in a "background" location yielded lead concentrations of 100, 150, 200, 250, and 300 mg/Kg. A simple random sample of soils at a nearby industrial site yielded lead concentrations of 100, 300, 800, and 1200 mg/Kg.
Test, with 95% confidence, whether these samples may have come from the same underlying Normally distributed population of lead concentrations. Use the t-table below. It shows values of upper percentage points of Student's t distribution for 3, 4, ..., 9 degrees of freedom (df).
| Alpha | |||
|
df |
90% | 95% | 97.5% |
| 3 | 1.638 | 2.353 | 3.182 |
| 4 | 1.533 | 2.132 | 2.776 |
| 5 | 1.476 | 2.015 | 2.571 |
| 6 | 1.440 | 1.943 | 2.447 |
| 7 | 1.415 | 1.895 | 2.365 |
| 8 | 1.397 | 1.860 | 2.306 |
| 9 | 1.383 | 1.833 | 2.262 |
2. Why are these test results invalid?
Scoring: The passing score is 90.
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This page was created 28 March 2001.