Case Study

Based on these scenarios, decide whether each researcher should specify a one-tailed or two-tailed test for their correlation coefficient and justify your choices based on their theoretical predictions.

Case context: A researcher is planning a study to investigate the relationship between self-esteem and academic performance. They have read extensive literature suggesting that as self-esteem increases, academic performance also tends to increase. However, another researcher in their lab is studying the relationship between favorite color and academic performance, and has no theoretical reason to predict a specific direction for any potential relationship.

Question: Based on these scenarios, decide whether each researcher should specify a one-tailed or two-tailed test for their correlation coefficient and justify your choices based on their theoretical predictions.

Sample answer: The first researcher should specify a one-tailed test because they theoretically predict the relationship will be strictly positive. The second researcher should specify a two-tailed test because they do not expect a specific direction for the relationship between the variables.

Key points:

  • One-tailed tests are specified when a researcher theoretically predicts a relationship will be strictly positive or strictly negative.
  • Two-tailed tests are specified when a researcher has no expectation about the direction of the relationship.
  • The first scenario requires a one-tailed test due to the predicted positive direction.
  • The second scenario requires a two-tailed test because no specific direction is expected.

Rubric: Students must correctly associate the directional prediction with a one-tailed test and the lack of a directional expectation with a two-tailed test.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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