Table 3.

Variances for matched pairs comparisons.

Statistic	Variance	Estimate of variance
risk difference (general)*
risk difference (null)**
log risk ratio (general) †
log odds ratio (general) ‡

*Altman et al. [11], p.52.

**Fleiss, Levin and Paik [12], p.375.

^†Væth and Poulsen [13]

^‡ Rothman and Greenland [14], p.286