Which statement about directional hypotheses is correct?

Which statement about directional hypotheses is correct?

• A. A directional hypothesis specifies the expected direction of the effect.
• B. A directional hypothesis states there will be no difference.
• C. A directional hypothesis requires meta-analysis.
• D. A directional hypothesis is unrelated to one-tailed tests.

Answer: (A)

A directional hypothesis specifies the expected direction of the effect, such as predicting that one group will score higher (or lower) than another. This kind of statement is tested with a one-tailed test because you’re looking for evidence in a specific direction. It increases power to detect an effect in the predicted direction, but if the effect appears in the opposite direction you may not find it significant. The other ideas don’t fit as well. Saying there will be no difference describes a null hypothesis, not a directional one. Meta-analysis is a method for combining results across studies, not a feature of the hypothesis itself. And a directional hypothesis is inherently linked to one-tailed testing, not unrelated to it.

A directional hypothesis specifies the expected direction of the effect, such as predicting that one group will score higher (or lower) than another. This kind of statement is tested with a one-tailed test because you’re looking for evidence in a specific direction. It increases power to detect an effect in the predicted direction, but if the effect appears in the opposite direction you may not find it significant.

The other ideas don’t fit as well. Saying there will be no difference describes a null hypothesis, not a directional one. Meta-analysis is a method for combining results across studies, not a feature of the hypothesis itself. And a directional hypothesis is inherently linked to one-tailed testing, not unrelated to it.