Table 4.

Sample sizes for superiority study designs. The hypothesis is that the new modulator is more efficacious than a comparator (either placebo or an active comparator)

	Anticipated FEV1 treatment effect: New modulator−comparator (%)	SD of the change in FEV1 % predicted*	Sample size per group†
Scenario A	3	7.3	125
Scenario B	5	7.3	45
Scenario C	10	7.3	12

Scenarios estimate the sample size for a 1:1 randomised study with a primary endpoint of absolute change in FEV₁% predicted.

*SDs approximated from the 6-month changes in FEV₁ observed in previous trials.^{16 21}

†Estimated using a two-sample t test assuming 90% power and a two-sided 0.05 level of significance.