{"id":11676,"date":"2018-07-24T02:44:14","date_gmt":"2018-07-24T07:44:14","guid":{"rendered":"https:\/\/www.invespcro.com\/blog\/?p=11676"},"modified":"2026-08-10T17:34:44","modified_gmt":"2026-08-10T17:34:44","slug":"one-tailed-vs-two-tailed-a-b-testing-everything-you-possibly-need-to-know","status":"publish","type":"post","link":"https:\/\/www.invespcro.com\/blog\/one-tailed-vs-two-tailed-a-b-testing-everything-you-possibly-need-to-know\/","title":{"rendered":"One-tailed vs. Two-tailed Tests &#8211;  Everything You Possibly Need to Know One-tailed vs. Two-tailed A\/B Testing"},"content":{"rendered":"<span class=\"span-reading-time rt-reading-time\" style=\"display: block;\"><span class=\"rt-label rt-prefix\">Reading Time: <\/span> <span class=\"rt-time\"> 16<\/span> <span class=\"rt-label rt-postfix\">minutes<\/span><\/span>\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"11676\" class=\"elementor elementor-11676\" data-elementor-post-type=\"post\">\n\t\t\t\t\t\t<section class=\"elementor-section elementor-top-section elementor-element elementor-element-1b374898 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-id=\"1b374898\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-7d93f1da\" data-id=\"7d93f1da\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-114efa79 elementor-widget elementor-widget-text-editor\" data-id=\"114efa79\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>I have meant to write this post for a long time. There has been a lot written about one-tailed vs. two-tailed tests. However, most of the articles approach the topic from a purely statistical perspective providing many formulas but do not show how to do the calculations. Others articles approach the issue from a high-level business perspective. So, here is my attempt to delve deep into the topic. Some sections in this article are heavy on stats and formulas. If you are not interested in these, you can skip them! Special thanks to our data sciences team that checked and rechecked the math on the article.<\/p><p>Most <a href=\"https:\/\/www.invespcro.com\/ab-testing\/vs-multivariate-testing\/\">A\/B testing platforms<\/a> do not provide the option to choose between one-tailed vs. two-tailed analysis. Moreover, until 2015, several popular testing platforms relied on one-tailed in statistical analysis.<\/p><p>The same applies to many other disciplines where having to choose between a one-tailed vs. two-tailed is rarely encountered since the majority of statistical software only offers two-tailed analysis as the single option.<\/p><p style=\"text-align: left;\">There is a common belief that two-tailed tests are generally \u201cbetter\u201d in some way, leading to more accurate and more reliable results.<\/p><p style=\"text-align: left;\">This is an apparent misconception.<\/p><\/div><\/div><\/div><\/div><\/div><\/section><\/div> <a href=\"https:\/\/www.invespcro.com\/blog\/one-tailed-vs-two-tailed-a-b-testing-everything-you-possibly-need-to-know\/#more-11676\" class=\"more-link elementor-more-link\"><span aria-label=\"Continue reading One-tailed vs. Two-tailed Tests &#8211;  Everything You Possibly Need to Know One-tailed vs. Two-tailed A\/B Testing\">(more&hellip;)<\/span><\/a>","protected":false},"excerpt":{"rendered":"<p><span class=\"span-reading-time rt-reading-time\" style=\"display: block;\"><span class=\"rt-label rt-prefix\">Reading Time: <\/span> <span class=\"rt-time\"> 16<\/span> <span class=\"rt-label rt-postfix\">minutes<\/span><\/span>I have meant to write this post for a long time. There has been a lot written about one-tailed vs. two-tailed tests. However, most of the articles approach the topic from a purely statistical perspective providing many formulas but do not show how to do the calculations. Others articles approach the issue from a high-level [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":11728,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[116,36],"tags":[245,593,109,594],"class_list":["post-11676","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-ab-testing","category-cro","tag-intermediate","tag-one-tailed","tag-resource","tag-two-tailed"],"_links":{"self":[{"href":"https:\/\/www.invespcro.com\/blog\/wp-json\/wp\/v2\/posts\/11676","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.invespcro.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.invespcro.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.invespcro.com\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.invespcro.com\/blog\/wp-json\/wp\/v2\/comments?post=11676"}],"version-history":[{"count":3,"href":"https:\/\/www.invespcro.com\/blog\/wp-json\/wp\/v2\/posts\/11676\/revisions"}],"predecessor-version":[{"id":100995,"href":"https:\/\/www.invespcro.com\/blog\/wp-json\/wp\/v2\/posts\/11676\/revisions\/100995"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.invespcro.com\/blog\/wp-json\/wp\/v2\/media\/11728"}],"wp:attachment":[{"href":"https:\/\/www.invespcro.com\/blog\/wp-json\/wp\/v2\/media?parent=11676"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.invespcro.com\/blog\/wp-json\/wp\/v2\/categories?post=11676"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.invespcro.com\/blog\/wp-json\/wp\/v2\/tags?post=11676"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}