Which statement best describes the interpretation of a treatment effect size greater than 0.8?

Which statement best describes the interpretation of a treatment effect size greater than 0.8?

• A. Small
• B. Large
• C. Moderate
• D. Very small

Answer: (B)

Interpreting the magnitude of a standardized treatment effect uses conventions like Cohen’s d, where small is about 0.2, moderate about 0.5, and large about 0.8. A value greater than 0.8 means the treatment group differs from the control by more than 0.8 standard deviations, indicating a substantial, noticeable difference. In practice, this is described as a large effect, signaling a meaningful impact of the treatment beyond random variation. Keep in mind that the exact interpretation can vary by field, but the threshold of 0.8 is the standard cue for a large effect.

Interpreting the magnitude of a standardized treatment effect uses conventions like Cohen’s d, where small is about 0.2, moderate about 0.5, and large about 0.8. A value greater than 0.8 means the treatment group differs from the control by more than 0.8 standard deviations, indicating a substantial, noticeable difference. In practice, this is described as a large effect, signaling a meaningful impact of the treatment beyond random variation. Keep in mind that the exact interpretation can vary by field, but the threshold of 0.8 is the standard cue for a large effect.