[I&#x27;m a PM @ Optimizely]<p>We were asked about this article before, on our community forums, and one of our statisticians, David, wrote a detailed reply to this article&#x27;s concerns about one- vs two-tailed testing, which might be of interest [3rd from the top]:<p><a href="https:&#x2F;&#x2F;community.optimizely.com&#x2F;t5&#x2F;Strategy-Culture&#x2F;Let-s-talk-about-Single-Tailed-vs-Double-Tailed&#x2F;m-p&#x2F;4220" rel="nofollow">https:&#x2F;&#x2F;community.optimizely.com&#x2F;t5&#x2F;Strategy-Culture&#x2F;Let-s-t...</a><p>Additionally, since then, as other commenters have mentioned, we&#x27;ve completely overhauled how we do our A&#x2F;B-testing calculations, which, theoretically and empirically, now have an accurate false-positive rate even when monitored continuously.  Details:<p><a href="https:&#x2F;&#x2F;blog.optimizely.com&#x2F;2015&#x2F;01&#x2F;20&#x2F;statistics-for-the-internet-age-the-story-behind-optimizelys-new-stats-engine&#x2F;" rel="nofollow">https:&#x2F;&#x2F;blog.optimizely.com&#x2F;2015&#x2F;01&#x2F;20&#x2F;statistics-for-the-in...</a>