{"id":774,"date":"2025-12-23T10:12:56","date_gmt":"2025-12-23T10:12:56","guid":{"rendered":"https:\/\/alandix.com\/statistics\/?page_id=774"},"modified":"2025-12-23T10:16:04","modified_gmt":"2025-12-23T10:16:04","slug":"chapter-10","status":"publish","type":"page","link":"https:\/\/alandix.com\/statistics\/book\/toc\/chapter-10\/","title":{"rendered":"Chapter 10: Gaining power &#8212; the dreaded &#8216;too few participants&#8217;"},"content":{"rendered":"<div class=\"embedurl\" data-url=\"https:\/\/alandix.com\/books\/hcistats\/content1e\/chaps\/chap-10.html\" ><!--  Chapter 10 Gaining power \u2013 the dreaded \u2018too few participants\u2019   -->\n\n<script>\nvar chapnos = 10;\nvar json_url = \"https:\\\/\\\/alandix.com\\\/books\\\/hcistats\\\/content1e\\\/chaps\\\/chap-10.json\";\n<\/script>\n\n\n\n\n\n\n<h3> Contents <\/h3>\n<div class=\"toc\">\n<dl>\n<dt>10.1&nbsp;&nbsp;If there is something there, make sure you find it <\/dt>\n<dt>10.2&nbsp;&nbsp;The noise&ndash;effect&ndash;number triangle <\/dt><dd><dl>\n<dt>10.2.1&nbsp;&nbsp;General strategies <\/dt>\n<\/dl><\/dd>\n<dt>10.3&nbsp;&nbsp;Subjects <\/dt><dd><dl>\n<dt>10.3.1&nbsp;&nbsp;More subjects or trials (increase number) <\/dt>\n<dt>10.3.2&nbsp;&nbsp;Within-subjects\/within-groups studies (reduce noise) <\/dt>\n<dt>10.3.3&nbsp;&nbsp;Matched users (reduce noise) <\/dt>\n<dt>10.3.4&nbsp;&nbsp;Targeted user group (increase effect) <\/dt>\n<\/dl><\/dd>\n<dt>10.4&nbsp;&nbsp;Tasks <\/dt><dd><dl>\n<dt>10.4.1&nbsp;&nbsp;Distractor tasks (increase effect) <\/dt>\n<dt>10.4.2&nbsp;&nbsp;Targeted tasks (increase effect) <\/dt>\n<dt>10.4.3&nbsp;&nbsp;Demonic interventions! (increase effect) <\/dt>\n<dt>10.4.4&nbsp;&nbsp;Restricted tasks (reduce noise) <\/dt>\n<\/dl><\/dd>\n<\/dl><\/div>\n\n\n<h3> Glossary items referenced in this chapter <\/h3>\n<div class=\"toc\">\n<a href=\"https:\/\/alandix.com\/glossary\/hcistats\/a-b%20test\">A&amp;ndash;B test<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/alternative%20hypothesis\">alternative hypothesis<\/a>, <strong><a href=\"https:\/\/alandix.com\/glossary\/hcistats\/balance%20orders\">balance orders<\/a><\/strong>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/bayesian%20statistics\">Bayesian statistics<\/a>, <strong><a href=\"https:\/\/alandix.com\/glossary\/hcistats\/between-subjects%20design\">between-subjects design<\/a><\/strong>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/cognitive%20load\">cognitive load<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/control%20conditions\">control conditions<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/controlled%20environments\">controlled environments<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/controlled%20experiment\">controlled experiment<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/controlled%20tasks\">controlled tasks<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/coping%20mechanisms\">coping mechanisms<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/demonic%20intervention\">demonic intervention<\/a>, <strong><a href=\"https:\/\/alandix.com\/glossary\/hcistats\/distractor%20task\">distractor task<\/a><\/strong>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/ecological%20validity\">ecological validity<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/effect%20size\">effect size<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/elderly%20users\">elderly users<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/error%20bars\">error bars<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/expert%20slip\">expert slip<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/false%20baseline\">false baseline<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/false%20negative\">false negative<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/false%20positive\">false positive<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/fitts%27%20law\">Fitts&#039; Law<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/five%20users\">five users (the myth)<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/formative%20evaluation\">formative evaluation<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/hci\">Human&amp;ndash;Computer Interaction<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/hci%20studies\">HCI studies<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/hypothesis%20testing\">hypothesis testing<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/image%20recognition\">image recognition<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/in-the-wild\">in-the-wild<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/increase%20effect\">increase effect<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/increase%20number\">increase number<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/individual%20differences\">individual differences<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/iterative%20development\">iterative development<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/learning%20effects\">learning effects<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/manipulate%20the%20sensitivity\">manipulate the sensitivity<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/matching%20subjects\">matching subjects<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/mathematics\">mathematics<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/mean\">mean (&amp;mu;)<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/menu%20navigation\">menu navigation<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/muller-lyer%20illusion\">M&amp;uuml;ller&amp;ndash;Lyer illusion<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/narrow%20user%20group\">narrow user group<\/a>, <strong><a href=\"https:\/\/alandix.com\/glossary\/hcistats\/noise-effect-number%20triangle\">noise&amp;ndash;effect&amp;ndash;number triangle<\/a><\/strong>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/nonlinearity\">nonlinearity<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/not%20significant\">not significant<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/null%20hypothesis\">null hypothesis<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/order%20effects\">order effects<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/pair%20subjects\">pair subjects<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/parameters\">parameters<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/power-law%20distribution\">power-law distribution<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/presidential%20inauguration\">presidential inauguration<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/random%20noise\">random noise<\/a>, <strong><a href=\"https:\/\/alandix.com\/glossary\/hcistats\/randomise%20orders\">randomise orders<\/a><\/strong>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/real%20world\">real world<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/reduce%20noise\">reduce noise<\/a>, <strong><a href=\"https:\/\/alandix.com\/glossary\/hcistats\/restricted%20device\">restricted device<\/a><\/strong>, <strong><a href=\"https:\/\/alandix.com\/glossary\/hcistats\/restricted%20system\">restricted system<\/a><\/strong>, <strong><a href=\"https:\/\/alandix.com\/glossary\/hcistats\/restricted%20tasks\">restricted tasks<\/a><\/strong>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/sample\">sample<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/size%20of%20the%20%60noise%27\">size of the `noise&#039;<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/size%20of%20the%20study\">size of the study<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/social%20network%20data\">social network data<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/sonic%20enhancement\">sonic enhancement<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/standard%20deviation\">standard deviation (s.d., &amp;sigma;)<\/a>, <strong><a href=\"https:\/\/alandix.com\/glossary\/hcistats\/standard%20error\">standard error (s.e.)<\/a><\/strong>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/statistical%20analysis\">statistical analysis<\/a>, <strong><a href=\"https:\/\/alandix.com\/glossary\/hcistats\/statistical%20power\">statistical power<\/a><\/strong>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/statistically%20significant\">statistically significant<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/steering%20task\">steering task<\/a>, <strong><a href=\"https:\/\/alandix.com\/glossary\/hcistats\/subjects\">subjects<\/a><\/strong>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/summative%20evaluation\">summative evaluation<\/a>, <strong><a href=\"https:\/\/alandix.com\/glossary\/hcistats\/targeted%20tasks\">targeted tasks<\/a><\/strong>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/targeted%20user%20group\">targeted user group<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/task%20completion%20time\">task completion time<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/tasks\">tasks<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/the%20job%20of%20statistics\">the job of statistics<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/uncontrolled%20factors\">uncontrolled factors<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/uncontrolled%20variation\">uncontrolled variation<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/user%20experience\">user experience<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/user%20experience%20studies\">user experience studies<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/user%20studies\">user studies<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/variability\">variability<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/weird%20people\">WEIRD people<\/a>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/within-groups%20studies\">within-groups studies<\/a>, <strong><a href=\"https:\/\/alandix.com\/glossary\/hcistats\/within-subjects%20experiment\">within-subjects experiment<\/a><\/strong>, <a href=\"https:\/\/alandix.com\/glossary\/hcistats\/wizard%20of%20oz%20prototyping\">Wizard of Oz prototyping<\/a><\/div>\n\n\n<!-- ?php\n\tif ( @$page['prolog_examples'] ):\n?>\n<h3> Prolog examples (from 1st ed.) <\/h3>\n<!-- ?php\n\techo $page['prolog_examples'];\n?>\n<!-- ?php\n\tendif; \/\/ @$page['prolog_examples']\n? -->\n\n<\/div>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":2,"featured_media":0,"parent":759,"menu_order":10,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_themeisle_gutenberg_block_has_review":false,"footnotes":""},"class_list":["post-774","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/alandix.com\/statistics\/wp-json\/wp\/v2\/pages\/774","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/alandix.com\/statistics\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/alandix.com\/statistics\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/alandix.com\/statistics\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/alandix.com\/statistics\/wp-json\/wp\/v2\/comments?post=774"}],"version-history":[{"count":2,"href":"https:\/\/alandix.com\/statistics\/wp-json\/wp\/v2\/pages\/774\/revisions"}],"predecessor-version":[{"id":795,"href":"https:\/\/alandix.com\/statistics\/wp-json\/wp\/v2\/pages\/774\/revisions\/795"}],"up":[{"embeddable":true,"href":"https:\/\/alandix.com\/statistics\/wp-json\/wp\/v2\/pages\/759"}],"wp:attachment":[{"href":"https:\/\/alandix.com\/statistics\/wp-json\/wp\/v2\/media?parent=774"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}