In meta-analysis, what is the meaningfully quantitative index used to summarize results across studies?

In meta-analysis, what is the meaningfully quantitative index used to summarize results across studies?

• A. p-value
• B. Confidence interval
• C. Effect size
• D. Correlation coefficient

Answer: (C)

The key idea in meta-analysis is that you need a single, comparable measure of how large the effect is across many studies. That measure is the effect size, because it quantifies the magnitude of the intervention or association on a common scale, allowing results from different studies to be combined meaningfully. P-values tell you whether an effect could be due to chance in individual studies, but they don’t indicate how big the effect is across studies. Confidence intervals describe the precision around an estimated effect, not the summary metric itself. The correlation coefficient measures the strength of a relationship within a study, and while related concepts can appear in meta-analytic work, the standard practice for summarizing across studies is to use an effect size (like a standardized mean difference, odds ratio, or risk ratio) that can be pooled.

The key idea in meta-analysis is that you need a single, comparable measure of how large the effect is across many studies. That measure is the effect size, because it quantifies the magnitude of the intervention or association on a common scale, allowing results from different studies to be combined meaningfully. P-values tell you whether an effect could be due to chance in individual studies, but they don’t indicate how big the effect is across studies. Confidence intervals describe the precision around an estimated effect, not the summary metric itself. The correlation coefficient measures the strength of a relationship within a study, and while related concepts can appear in meta-analytic work, the standard practice for summarizing across studies is to use an effect size (like a standardized mean difference, odds ratio, or risk ratio) that can be pooled.