A study evaluates whether pairing twins on a treatment reduces the standard error of the estimated effect.
Why does pairing typically reduce variability of the estimated effect?
- A
It guarantees equal variances.
- B
It increases the sample size.
- C
It eliminates the need for randomization.
- Dcheck_circle
It removes between-pair variation from the comparison.
Explanation
Differences within pairs control for between-pair characteristics, lowering the SE of the mean difference.