Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
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);
}
@mysticaltech

This comment has been minimized.

Copy link

@mysticaltech mysticaltech commented Apr 3, 2020

This is missing from the part before the declaration of t_alpha2, see https://www.evanmiller.org/ab-testing/sample-size-fixed.js

if (p > 0.5) {
        p = 1.0 - p;
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.