{"id":9525,"date":"2025-03-01T13:55:59","date_gmt":"2025-03-01T18:55:59","guid":{"rendered":"https:\/\/dhss.delaware.gov\/dph\/significance_layreader\/"},"modified":"2025-03-02T00:25:11","modified_gmt":"2025-03-02T05:25:11","slug":"significance_layreader","status":"publish","type":"page","link":"https:\/\/dhss.delaware.gov\/dph\/dpc\/significance_layreader\/","title":{"rendered":"dpc\/significance_layreader ~  What is Statistical Significance?  &#8211; Delaware Health and Social Services &#8211; State of Delaware"},"content":{"rendered":"<div data-swiftype-index=\"true\">\n\n\n\n\n\n  <br>\n\n\n  \n\n\n  <div class=\"container\" id=\"main_header\">\n\n\n    <!-- BEGIN readspeaker div -->\n\n\n    <div class=\"rs_skip rsbtn rs_preserve\" id=\"readspeaker_button1\">\n\n\n      <a accesskey=\"L\" class=\"rsbtn_play\" href=\"https:\/\/app-na.readspeaker.com\/cgi-bin\/rsent?customerid=7262&#038;lang=en_us&#038;readid=main_content&#038;url=https:\/\/dhss.delaware.gov\/dph\/dpc\/significance_layreader.html\" title=\"Listen to this page using ReadSpeaker\">\n\n\n        <span class=\"rsbtn_left rsimg rspart\"><span class=\"rsbtn_text\"><span>Listen<\/span><\/span><\/span>\n\n\n        <span class=\"rsbtn_right rsimg rsplay rspart\"><\/span>\n\n\n      <\/a>\n\n\n    <\/div>\n\n\n    <!-- END readspeaker div -->\n\n\n\n\n\n    \n\n\n    <header class=\"pull-left\">\n\n\n      <h1><!--[type=EDIT name=\"Page Title\"]--><\/h1><h1>What Is the Meaning <br> of &#8220;Statistical Significance&#8221;?<\/h1><h1><!--[END]--><\/h1>\n\n\n    <\/header>\n\n\n  <\/div><br>\n\n\n \n\n\n  <div class=\"container\">\n\n\n    <div class=\"row\">\n\n\n      <div class=\"col-md-3\" id=\"leftCol\">\n\n\n        <div class=\"panel-group\" id=\"accordion\">\n\n\n          <div class=\"panel sectionmenu_panel\">\n\n\n            <div class=\"panel-heading\">\n\n\n              <p class=\"panel-title\"><a class=\"agency_nav\" data-parent=\"#accordion\" data-toggle=\"collapse\" href=\"#collapseOne\"><strong><i class=\"fa fa-align-justify fa-fw\"><\/i> Public Health Menu<\/strong><\/a><\/p>\n\n\n            <\/div>\n\n\n\n\n\n            <div class=\"panel-collapse collapse in\" id=\"collapseOne\">\n\n\n              <div class=\"panel-body\" id=\"clf_nav\">\n\n\n                  <ul class=\"nav nav-stacked nav-pills-clf\" id=\"agency_sidebar\">\n    <li><a href=\"\/dph\/\"><h2>Home <i class=\"fa fa-home fa-fw\"><\/i><\/h2><\/a><\/li>\n    <li class=\"toplevel\"><a data-parent=\"#agency_sidebar\" data-toggle=\"collapse\" href=\"#HomeMenu\"><h2>About <i class=\"fa fa-caret-right fa-fw\"><\/i><\/h2><\/a>\n      <ul class=\"panel-collapse collapse\" id=\"HomeMenu\">\n        <li><a href=\"\/dph\/about.html\">About DPH<\/a><\/li>\n        <li><a href=\"\/dph\/sections.html\">Sections &#038; 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height: 394px; margin-left: 15px; margin-right: 15px;\"><\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n<p>The graph above illustrates how prevalence estimates can vary from year to year, without the difference being statistically significant.\u00a0 There was no actual change in prevalence between 2013 and 2017.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n<p>Each prevalence estimate has a \u201cconfidence interval\u201d \u2013 a range in which you can be 95 percent confident the actual prevalence falls. As long as the confidence intervals overlap, survey researchers feel confident there has been no change or difference in prevalence.\u00a0\u00a0 A \u201c95 percent confidence level\u201d means that if the survey were conducted 100 times, 95 of the surveys would report responses within the same confidence intervals.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n<p>If the confidence intervals do <strong><em>not<\/em><\/strong> overlap, there likely has been a real change, and we refer to that as a \u201cstatistically significant\u201d difference.\u00a0 If we see statistically significant differences, or if we see a steady trend upward or downward over a period of several years, we can say with some confidence that the prevalence is changing.\u00a0<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n<p>For example, if a prevalence goes up by only 1 percentage point \u2013 and that is well within the confidence interval \u2013 we cannot say there has been any increase or change.\u00a0 In that situation, the prevalence is statistically unchanged.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n<p>The chart below, showing the prevalence of adult Delawareans who are overweight but not obese, demonstrates a difference between New Castle and Sussex counties which is not statistically significant, because the confidence intervals (CI) overlap.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n<div>\n\n\n\n\n\n\n\n<table align=\"center\" border=\"1\" cellpadding=\"1\" cellspacing=\"1\" style=\"width:500px;\" summary=\"This chart shows confidence intervals which overlap, therefore the prevalence estimates are not statistically significantly different.\">\n\n\n\n\n\n\n\n <caption><strong>No Statistically Significant Difference<\/strong><\/caption>\n\n\n\n\n\n\n\n <tbody>\n\n\n\n\n\n\n\n  <tr>\n\n\n\n\n\n\n\n   <td>\u00a0<\/td>\n\n\n\n\n\n\n\n   <td style=\"text-align: center;\"><strong><span style=\"background-color:#00FFFF;\">New Castle County<\/span><\/strong><\/td>\n\n\n\n\n\n\n\n   <td style=\"text-align: center;\"><strong><span style=\"background-color:#00FFFF;\">Sussex County<\/span><\/strong><\/td>\n\n\n\n\n\n\n\n  <\/tr>\n\n\n\n\n\n\n\n  <tr>\n\n\n\n\n\n\n\n   <td>Overweight Adults<\/td>\n\n\n\n\n\n\n\n   <td>\n\n\n\n\n\n\n\n   <p style=\"text-align: center;\"><strong>37.6%<\/strong><\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n   <p style=\"text-align: center;\">CI = 34.3 &#8211; 40.9%)<\/p>\n\n\n\n\n\n\n\n   <\/td>\n\n\n\n\n\n\n\n   <td>\n\n\n\n\n\n\n\n   <p style=\"text-align: center;\"><strong>38.8%<\/strong><\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n   <p style=\"text-align: center;\">CI = 34.9 &#8211; 42.7%)<\/p>\n\n\n\n\n\n\n\n   <\/td>\n\n\n\n\n\n\n\n  <\/tr>\n\n\n\n\n\n\n\n <\/tbody>\n\n\n\n\n\n\n\n<\/table>\n\n\n\n\n\n\n\n<\/div>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n<h2>Definitions<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n<p><strong>Prevalence<\/strong>:\u00a0 the percentage of a population that is affected with a particular disease, condition or behavior at a given time, in this case a calendar year. \u00a0Prevalence should not be confused with \u201cincidence,\u201d which refers to the occurrence of new cases. \u00a0Incidence\u00a0relates to the risk of contracting a\u00a0disease, whereas prevalence indicates how widespread the\u00a0disease or condition is in a population.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n<p><strong>95 percent confidence level<\/strong>:\u00a0 When a survey is conducted at the 95 percent confidence level, there is a very high level of confidence that the results are valid.\u00a0 If the survey were conducted 100 times, 95 of the surveys\u2019 responses would lie within the same range.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n<p><strong>Confidence interval<\/strong>:\u00a0 the range of estimates within which the actual prevalence can be found.\u00a0 For example, the 2017 prevalence for adult cigarette smoking was 17 percent.\u00a0 The confidence interval, the range within which that estimate lies, was 15.3 percent to 18.7 percent.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n<p><strong>Statistical significance<\/strong>: the likelihood that a relationship between two prevalence variables is caused by something other than chance.\u00a0 There are several tests for statistical significance.\u00a0 At the most basic level, if confidence intervals do not overlap the difference is likely \u201cstatistically significant.\u201d\u00a0 Other analyses can be done if necessary \u2013 or, for example, to check for significance when age-adjusting data.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n<p>\u00a0<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n<hr>\n\n\n\n\n\n\n\n<p><span style=\"font-size:11px;\"><strong><a href=\"brfsurveys.html\">Return to the main Delaware BRFS page.<\/a><\/strong><\/span><\/p>  <!--[END]-->\n\n\n  \n\n\n      <\/div>\n\n\n    <\/div>\n\n\n  <\/div><!-- \/container -->\n\n\n<\/div>","protected":false},"excerpt":{"rendered":"<p>Listen What Is the Meaning of &#8220;Statistical Significance&#8221;? 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