{"id":4590,"date":"2026-08-11T11:49:11","date_gmt":"2026-08-11T09:49:11","guid":{"rendered":"https:\/\/ellistat.com\/?post_type=guide-dutilisateur&#038;p=4590"},"modified":"2026-08-11T11:49:11","modified_gmt":"2026-08-11T09:49:11","slug":"power","status":"publish","type":"guide-dutilisateur","link":"https:\/\/ellistat.com\/en\/guide-dutilisateur\/puissance\/","title":{"rendered":"Power"},"content":{"rendered":"<p class=\"wp-block-paragraph\">Power is the probability of&nbsp;<strong>detect a discrepancy that actually exists<\/strong>. Its complement is the&nbsp;<strong>beta risk<\/strong>&nbsp;: to overlook a real difference.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This page relates four quantities, three of which determine the fourth:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>the\u00a0<strong>sample size<\/strong>\u00a0;<\/li>\n\n\n\n<li>the\u00a0<strong>tested difference<\/strong>\u00a0: the difference you want to be able to detect; ;<\/li>\n\n\n\n<li>dispersion: <strong>sigma<\/strong>, or the\u00a0<strong>sigma ratio<\/strong>\u00a0;<\/li>\n\n\n\n<li>the\u00a0<strong>risks<\/strong>\u00a0alpha and beta.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Tests covered:\u00a0<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Test Z<\/strong>\u00a0and\u00a0<strong>T Test<\/strong>\u00a0compared to a theoretical value,\u00a0<\/li>\n\n\n\n<li><strong>T Test<\/strong>\u00a0To compare two means,\u00a0<\/li>\n\n\n\n<li><strong>Paired T-test<\/strong>,\u00a0<\/li>\n\n\n\n<li><strong>ANOVA<\/strong>\u00a0for several averages,\u00a0<\/li>\n\n\n\n<li><strong>Chi-Square Test<\/strong>\u00a0and\u00a0<strong>Test F<\/strong>\u00a0on standard deviations,\u00a0<\/li>\n\n\n\n<li><strong>Test 1P<\/strong>\u00a0and\u00a0<strong>Test 2P<\/strong>\u00a0on proportions. <\/li>\n\n\n\n<li>One section covers the\u00a0<strong>2k design of experiments<\/strong>, depending on the number of factors, the number of rows, and the number of second-order terms.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Example: Calculate the sample size needed to detect a difference of 15% to 5% between two lots: (answer: 111 units in each lot)<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"892\" height=\"762\" src=\"https:\/\/ellistat.com\/wp-content\/uploads\/puissance.png\" alt=\"\" class=\"wp-image-4591\" srcset=\"https:\/\/ellistat.com\/wp-content\/uploads\/puissance.png 892w, https:\/\/ellistat.com\/wp-content\/uploads\/puissance-300x256.png 300w, https:\/\/ellistat.com\/wp-content\/uploads\/puissance-768x656.png 768w, https:\/\/ellistat.com\/wp-content\/uploads\/puissance-14x12.png 14w\" sizes=\"auto, (max-width: 892px) 100vw, 892px\" \/><\/figure>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\ud83d\udca1&nbsp;<strong>This is the page you should open before the test, not after.<\/strong>&nbsp;It answers the question, \u00abHow many samples do I need to measure?\u00bb\u2014a question whose answer determines everything else. Conducting an undersized experiment guarantees a \u00abnot significant\u00bb result that proves nothing and will have to be repeated.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u26a0\ufe0f The implication is unpleasant but useful: detecting a small deviation is costly. Halving the detectable deviation quadruples the required sample size. It\u2019s best to know this before starting the tests.<\/p>\n<\/blockquote>","protected":false},"featured_media":0,"menu_order":50,"template":"","meta":{"_acf_changed":true},"menu-guide-dutilisateur":[23],"class_list":["post-4590","guide-dutilisateur","type-guide-dutilisateur","status-publish","hentry","menu-guide-dutilisateur-5-statistiques-inferentielles"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.2 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Puissance - Ellistat<\/title>\n<meta name=\"description\" content=\"Combien de pi\u00e8ces mesurer pour d\u00e9tecter un \u00e9cart r\u00e9el ? 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