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A researcher calculates a Pearson's correlation of r=.52r = -.52 with a sample of 22 participants (df=20df = 20). The critical value table lists the critical value for 20 degrees of freedom as .444 at the α=.05\alpha = .05 level. Apply the decision rule for critical values of rr to state whether the researcher can reject the null hypothesis and explain why.

Question: A researcher calculates a Pearson's correlation of r=.52r = -.52 with a sample of 22 participants (df=20df = 20). The critical value table lists the critical value for 20 degrees of freedom as .444 at the α=.05\alpha = .05 level. Apply the decision rule for critical values of rr to state whether the researcher can reject the null hypothesis and explain why.

Sample answer: Yes, the researcher can reject the null hypothesis. The calculated correlation of r=.52r = -.52 is more extreme (has a greater absolute value) than the critical value of .444, which means the result is statistically significant.

Key points:

  • Correctly apply the decision rule to reject the null hypothesis.
  • Explain that the calculated correlation coefficient (r=.52r = -.52) is more extreme than the critical value (.444).

Rubric: The student must state that the null hypothesis can be rejected and explain that the calculated value of .52-.52 is more extreme than the critical value threshold of .444.

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Updated 2026-05-26

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Research Methods in Psychology - 4th American Edition @ KPU

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