What is effect size?

What is effect size?

• A. provides a measurement of the absolute magnitude of a treatment effect, independent of sample size.
• B. the probability of finding a significant result.
• C. the p-value.
• D. the standard deviation of the treatment group.

Answer: (A)

Effect size is about the magnitude of the treatment effect, expressed in a way that does not depend on how many participants were studied. It tells you how large the difference or association is in practical terms, not just whether it exists. Common forms include Cohen’s d for differences between means, odds ratio or relative risk for binary outcomes, and correlation r for relationships. This stands in contrast to a p-value, which measures the probability of observing the data if the null hypothesis were true and tends to be influenced by sample size. It’s also different from a standard deviation, which describes variability rather than the size of the effect. So effect size provides a sense of how meaningful the treatment effect is in real-world terms.

Effect size is about the magnitude of the treatment effect, expressed in a way that does not depend on how many participants were studied. It tells you how large the difference or association is in practical terms, not just whether it exists. Common forms include Cohen’s d for differences between means, odds ratio or relative risk for binary outcomes, and correlation r for relationships. This stands in contrast to a p-value, which measures the probability of observing the data if the null hypothesis were true and tends to be influenced by sample size. It’s also different from a standard deviation, which describes variability rather than the size of the effect. So effect size provides a sense of how meaningful the treatment effect is in real-world terms.