[shawabawa3]

Of course if you are A/B testing something which doubles conversions from 25% to 50% (100% improvement) you'll know quickly. However, if you're looking at something which is better by something more realistic like taking conversions from 5% to 5.5%, you're looking at around 10000 visits each for 90% confidence.

[ryanglasgow]

A startup isn't looking to make tiny .5% increment improvements so I don't see how this is relevant. Companies looking to grow a small user base are making significant changes, seeking significant improvements.

[insickness]

Your average well-crafted sales page on the internet has a conversion rate of 2.5%. A 0.5% increment is a HUGE difference. You're lucky if you get a 0.2% increment after an extensive A/B test.