sanjeevpe

mottalrd / gist:7ddfd45d14bc7433dec2

Last active March 29, 2022 07:38

Evan Miller source code for sample size from my blog post http://www.alfredo.motta.name/ab-testing-from-scratch/

	function num_subjects(alpha, power_level, p, delta) {
	var t_alpha2 = ppnd(1.0-alpha/2);
	var t_beta = ppnd(power_level);

	var sd1 = Math.sqrt(2 * p * (1.0 - p));
	var sd2 = Math.sqrt(p * (1.0 - p) + (p + delta) * (1.0 - p - delta));

	return (t_alpha2 * sd1 + t_beta * sd2) * (t_alpha2 * sd1 + t_beta * sd2) / (delta * delta);
	}