{"id":2529,"date":"2020-10-12T12:23:34","date_gmt":"2020-10-12T11:23:34","guid":{"rendered":"https:\/\/www.snapsurveys.com\/support-snapxmp\/?post_type=epkb_post_type_1&#038;p=2529"},"modified":"2022-01-17T15:38:43","modified_gmt":"2022-01-17T15:38:43","slug":"statistical-significance-z-test","status":"publish","type":"epkb_post_type_1","link":"https:\/\/www.snapsurveys.com\/support-snapxmp\/snapxmp\/statistical-significance-z-test\/","title":{"rendered":"Statistical significance in tables (z-test)"},"content":{"rendered":"\n<p>\n  The z-test is used to compare two percentage scores to see if the difference between them is statistically significant. \n<\/p>\n\n\n\n<p>\n  This means: Is the difference in percentage scores in the table purely a result of the sample used, or does it indicate a real difference in percentages in the target population?\n<\/p>\n\n\n\n<p>\n  For each row in a table it compares the Break Percent for each column with all other columns. If more than one variable is included in the Break specification, the comparison will be among columns for the same variable only. That is, if \u201cAge\u201d and \u201cGender\u201d are specified as separate break variables, the individual columns within the age variable will only be compared with other columns for \u201cAge\u201d and not with the columns for \u201cGender\u201d.\n<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img fetchpriority=\"high\" decoding=\"async\" width=\"486\" height=\"379\" src=\"https:\/\/www.snapsurveys.com\/support-snapxmp\/wp-content\/uploads\/2020\/10\/ztest1-png.png\" alt=\"Example of an analysis table using z-test\" class=\"wp-image-2530\"\/><\/figure>\n\n\n\n<p>\n  Each cell of the table will contain the Break percent and a series of letters and hyphens. This is the output of the z-test and indicates which differences are significant and which are not significant, at the specified confidence levels.\n<\/p>\n\n\n\n<p>\n  The three possible characters and their meanings are:\n<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\n    A hyphen, meaning the difference is not statistically significant\n  <\/li><li>\n    A lower case letter indicating that the difference is statistically significant at the lower level specified\n  <\/li><li>\n    An upper case letter indicating that the difference is significant at the higher level specified.\n  <\/li><\/ul>\n\n\n\n<p>\n  The letters and hyphens refer, in order, to the other columns within the variable (A refers to the first column, B to the second column and so on). \n<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><a id=\"post-2529-_Toc35499153\"><\/a>Example: Adding the z-test to a table in the Crocodile survey<\/h2>\n\n\n\n<ol class=\"wp-block-list\"><li>\n  Click \n  <img decoding=\"async\" width=\"26\" height=\"26\" class=\"wp-image-2531\" alt=\"AnalysisTblIcon.png\" src=\"https:\/\/www.snapsurveys.com\/support-snapxmp\/wp-content\/uploads\/2020\/10\/analysistblicon-png-6.png\">\n   on the Snap toolbar to build a table\n<\/li><li>\n  Enter <strong>Q4<\/strong> (Items ordered)<strong> <\/strong>in the Analysis field.\n<\/li><li>\n  Enter <strong>Q11<\/strong> (Age) in the Break field.\n<\/li><li>\n  Check the Break Percents and <strong>z-test<\/strong> boxes on the right hand side. All other options should be clear.\n<\/li><\/ol>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" width=\"496\" height=\"410\" src=\"https:\/\/www.snapsurveys.com\/support-snapxmp\/wp-content\/uploads\/2020\/10\/ztest2-png.png\" alt=\"Analysis definition for a table using z-test\" class=\"wp-image-2532\"\/><\/figure>\n\n\n\n<ol class=\"wp-block-list\" start=\"5\"><li>\n  Click the <strong>Base\/Labels<\/strong> tab. Confirm that any missing values are excluded.\n<\/li><\/ol>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"293\" height=\"116\" src=\"https:\/\/www.snapsurveys.com\/support-snapxmp\/wp-content\/uploads\/2020\/10\/ztest3-png.png\" alt=\"Settings for the z-test\" class=\"wp-image-2533\"\/><\/figure>\n\n\n\n<ol class=\"wp-block-list\" start=\"6\"><li>\n  Click the <strong>Cells <\/strong>tab.\n<\/li><\/ol>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"469\" height=\"126\" src=\"https:\/\/www.snapsurveys.com\/support-snapxmp\/wp-content\/uploads\/2020\/10\/ztest4-png.png\" alt=\"Settings for z-tests\" class=\"wp-image-2534\"\/><\/figure>\n\n\n\n<ol class=\"wp-block-list\" start=\"7\"><li>   In the <strong>Body z-test<\/strong> section: <ul><li>Set the <strong>Upper Level<\/strong> to <strong>95<\/strong>% and the <strong>Lower Level<\/strong> to <strong>90<\/strong>% <\/li><li>Select <strong>2-Tail<\/strong>.  <\/li><li>Select <strong>All <\/strong>in the <strong>Show<\/strong> box.  <\/li><li>Check <strong>Hyphen<\/strong> and <strong>Index<\/strong> if these options are not already selected.  <\/li><li>Clear the <strong>Apply Yates Correction<\/strong> box. <\/li><\/ul><\/li><\/ol>\n\n\n\n<ol class=\"wp-block-list\" start=\"8\"><li>\n  Click <strong>OK<\/strong> to create the table.\n<\/li><\/ol>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"486\" height=\"379\" src=\"https:\/\/www.snapsurveys.com\/support-snapxmp\/wp-content\/uploads\/2020\/10\/ztest1-png-1.png\" alt=\"Example of an analysis table showing statistical significance (z-test)\" class=\"wp-image-2535\"\/><\/figure>\n\n\n\n<p>\n  If you look at the cell for the row labelled \u201cCoffee\/Tea\u201d and the column labelled \u201cC. 25-34\u201d the Z-Test output shows \u201cAb\u2011\u2011-\u201d. This indicates that the differences between this column (C) and column A is significant at the upper level (upper case letters), the difference between this column and column B is significant at the lower level (lower case letters) but the differences between this column and the columns D,E and F are not significant (hyphens). Note that there must be at least one hyphen in the output as a column cannot be significantly different from itself.\n<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The z-test is used to compare two percentage scores to see if the difference between them is statistically significant. This means: Is the difference in percentage scores in the table purely a result of the sample used, or does it indicate a real difference in percentages in the target population? For each row in a [&hellip;]<\/p>\n","protected":false},"author":7,"featured_media":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"epkb_post_type_1_category":[58],"epkb_post_type_1_tag":[],"class_list":["post-2529","epkb_post_type_1","type-epkb_post_type_1","status-publish","hentry","epkb_post_type_1_category-snap-tables"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v25.8 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Statistical significance in tables (z-test) | SnapSurveys<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.snapsurveys.com\/support-snapxmp\/snapxmp\/statistical-significance-z-test\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Statistical significance in tables (z-test) | SnapSurveys\" \/>\n<meta property=\"og:description\" content=\"The z-test is used to compare two percentage scores to see if the difference between them is statistically significant. 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