Sample sizes^* for two groups with 2∶1 allocation (Q = 2/3) to treatment versus control needed to provide 85% power to detect either a 50% difference, or an absolute difference of 0.2 pmol/ml, using either the raw or transformed data for an unstratified analysis at 12 or at 24 months.

*All computations are for a one-sided test at the 0.05 level with no adjustment for losses to follow-up. In all cases the 90% limits for the control group mean and the SD are used as the parameter values in equation (1). The exact N is provided as well as that rounded up to the nearest integer satisfying the 2∶1 allocation fractions.