\n\t1<\/td> | 2,475<\/td> | 3,142<\/td> | <\/td> | 9,894<\/td> | 12,562<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\n Table 2:<\/strong> Sample size requirements for various critical differences (two-tailed, 80% power, s<\/em> = 20. Between-subjects cells are the total sample size for a two-group study).<\/p>\nIf your SUS data has a standard deviation close to 17.7, use Table 1. If it\u2019s closer to 20, use Table 2. If it\u2019s in between, then you can interpolate the values in Tables 1 and 2 to get an idea about the approximate sample size. If you need a more precise estimate, see the following technical note.<\/p>\n Technical Note: If you\u2019re working with SUS data that has a very different standard deviation from 17.7 or 20, you can do a quick computation to adjust the values in these tables. The first step is to compute a multiplier by dividing the new target variance (s<\/em>2<\/sup>) by the variance used to create the table. Then multiply the tabled value of n by the multiplier and round it off to get the revised estimate. For example, if the target standard deviation (s<\/em>) is 19.1, the target variability (s<\/em>2<\/sup>) is 364.81. The variability from Table 2 is 400 (202<\/sup>), making the multiplier .912 (364.81\/400). To use this multiplier to adjust the sample size of 398 for 90% confidence and critical difference of 2.5 shown in Table 2 for a within-subjects design, multiply 398 by .912 and then round it off to 363. For a between-subjects design with the same requirements, multiply 1586 by .912 and round it off to 1,446 (723 per group).<\/p>\nSummary and Takeaways<\/h2>\nWhat sample size do you need when comparing two sets of SUS scores? To answer that question, you need several types of information, some common to all sample size estimation (confidence level to establish control of Type I errors, standard deviation, and margin of error or critical difference), others unique to statistical hypothesis testing (one- vs. two-tailed testing, setting a level of power to control Type II errors), and for comparison of means, whether the experimental design will be within- or between-subjects.<\/p>\n We provided two tables based on a typical standard deviation for the SUS in retrospective UX studies (s<\/em> = 17.7) and a more conservative standard deviation (s<\/em> = 20), with values for between- and within-subjects designs, 90% and 95% confidence, and power set to 80%.<\/p>\nFor UX researchers working in contexts where the typical standard deviation of the SUS might be different, we also provided a simple way to increase or decrease the tabled sample sizes for larger or smaller standard deviations.<\/p>\n","protected":false},"excerpt":{"rendered":" Microsoft Word is a widely used word processing program, part of the Microsoft Office suite of programs. While its dominance has been challenged recently by Google Docs, Word still leads on the features list, providing many features that Google\u2019s offering lacks. But adding features can also add to bloat, making common tasks harder as users […]<\/p>\n","protected":false},"author":1553,"featured_media":32358,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"site-sidebar-layout":"default","site-content-layout":"default","ast-site-content-layout":"","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"default","adv-header-id-meta":"","stick-header-meta":"default","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}},"_price":"field_56e41332a1ae5","_stock":"","_tribe_ticket_header":"","_tribe_default_ticket_provider":"Tribe__Tickets_Plus__Commerce__WooCommerce__Main","_tribe_ticket_capacity":"0","_ticket_start_date":"","_ticket_end_date":"","_tribe_ticket_show_description":"","_tribe_ticket_show_not_going":false,"_tribe_ticket_use_global_stock":"","_tribe_ticket_global_stock_level":"","_global_stock_mode":"","_global_stock_cap":"","_tribe_rsvp_for_event":"","_tribe_ticket_going_count":"","_tribe_ticket_not_going_count":"","_tribe_tickets_list":"[]","_tribe_ticket_has_attendee_info_fields":false,"footnotes":""},"categories":[121,43,39],"tags":[78,32,231,479,6],"acf":[],"ticketed":false,"_links":{"self":[{"href":"https:\/\/measuringu.com\/wp-json\/wp\/v2\/posts\/32285"}],"collection":[{"href":"https:\/\/measuringu.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/measuringu.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/measuringu.com\/wp-json\/wp\/v2\/users\/1553"}],"replies":[{"embeddable":true,"href":"https:\/\/measuringu.com\/wp-json\/wp\/v2\/comments?post=32285"}],"version-history":[{"count":27,"href":"https:\/\/measuringu.com\/wp-json\/wp\/v2\/posts\/32285\/revisions"}],"predecessor-version":[{"id":32367,"href":"https:\/\/measuringu.com\/wp-json\/wp\/v2\/posts\/32285\/revisions\/32367"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/measuringu.com\/wp-json\/wp\/v2\/media\/32358"}],"wp:attachment":[{"href":"https:\/\/measuringu.com\/wp-json\/wp\/v2\/media?parent=32285"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/measuringu.com\/wp-json\/wp\/v2\/categories?post=32285"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/measuringu.com\/wp-json\/wp\/v2\/tags?post=32285"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}} |