That is really awesome. One suggestion though: Make "relative" the default as well as set "1−β" to 90 or 95%. I assume that most people have a conversion rate

That is really awesome. One suggestion though: Make "relative" the default as well as set "1−β" to 90 or 95%. I assume that most people have a conversion rate of X, say 30%, and want to increase this by Y, say 20% (30% to 36%). If I consider the type of headline many blog posts and reports have, they are like "How we increased sales, trials, whatever by 50%". That's how they think. And well, I usually aim for 95% significance.