An environmentalist suggests that the median of the number of days per month that a large city failed to meet the EPA acceptable standards for clean air is 11 days per month. A random sample of 20 months shows the number of days per month that the air quality was below the EPA’s standards.

1. What is the claim?
2. What test would you use to test the claim? Why?
3. State the hypotheses.
4. Select a value for α and find the corresponding critical value.
5. What is the test statistic?
6. What is your decision?
7. Summarize the results.
8. Could a parametric test be used?

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