Significance tests

Practice sheet

Fresh questions from the whole chapter, to do on paper.

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  1. A company claims that 80% of customers are satisfied. A researcher suspects fewer are. Which is the null hypothesis?
    1. H₀: p = 0.80
    2. H₀: p < 0.80
    3. H₀: p̂ = 0.80
  2. The mean wait at a clinic used to be 81 minutes. A manager wants to know whether it has changed, in either direction. Which alternative?
    1. Hₐ: μ ≠ 81
    2. Hₐ: μ > 81
    3. Hₐ: x̄ ≠ 81
  3. Why are hypotheses written about parameters such as p, not statistics such as p̂ (sample of 445)?
    1. Because we know p̂ exactly; the question is about the unknown population value
    2. Because statistics are harder to compute
    3. There is no difference between p and p̂
  4. Test H₀: p = 0.5 with a random sample of 100 in which p̂ = 52/100. Find the z statistic.
  5. Test H₀: p = 0.2 with n = 400 and p̂ = 28/100. Find the z statistic.
  6. A test gives a P-value of 0.05. What does it mean?
    1. If H₀ were true, a result at least as extreme as ours would happen with probability 0.05
    2. There is a 0.05 probability that H₀ is true
    3. The result is due to chance with probability 0.05
  7. At significance level α = 0.05, a test gives P-value 0.04. What do you conclude?
    1. Reject H₀: there is convincing evidence for Hₐ
    2. Accept H₀
    3. Hₐ is proven true
  8. A test of a new drug (sample of 388) has H₀: the drug has no effect. What is a Type I error?
    1. Concluding the drug works when it really has no effect
    2. Concluding there is no effect when the drug really works
    3. Making a mistake in the data
  9. How can a researcher increase the power of a test that now uses 82 subjects?
    1. Use a larger sample
    2. Use a smaller α
    3. Use fewer subjects
  10. Test H₀: μ = 39. A random sample of 9 has x̄ = 43 and s = 9. Find the t statistic.
  11. A t test gives P-value 0.20. What can you conclude at α = 0.05?
    1. Fail to reject H₀: not enough evidence for Hₐ
    2. H₀ is true
    3. Reject H₀
  12. For a test statistic, the area in one tail beyond it is 0.04. Find the P-value of the two-sided test.