{"id":1215,"date":"2016-01-05T20:45:53","date_gmt":"2016-01-05T19:45:53","guid":{"rendered":"https:\/\/blogs.bmj.com\/adc\/?p=1215"},"modified":"2015-12-15T22:35:06","modified_gmt":"2015-12-15T21:35:06","slug":"statsminiblog-factor-analysis","status":"publish","type":"post","link":"https:\/\/blogs.bmj.com\/adc\/2016\/01\/05\/statsminiblog-factor-analysis\/","title":{"rendered":"StatsMiniBlog: Factor Analysis"},"content":{"rendered":"

\"calculator-97842_640\"<\/a>It’s another one of those things that you’ll see in a paper, often followed by the word “eigenvalue” and shudder, perhaps externally as well as internally.<\/p>\n

The’ll be a follow-up of ‘structure’ or the like after that, often fancifully named as different domains.<\/p>\n

The easiest (!) way to think of how it works is to take a questionnaire that asks about a range of different items – say all about what your symptoms and functional abilities are with a chronic lung disease. The maths then takes these items, and looks for those questions that between them explain the most of the variation in the\u00a0overall scores – this is the main factor. It then looks for another set of questions that explain more of the variation between answers (but not ‘re-explaining’ the stuff already looked at in factor 1 – i.e. ‘orthagonal’ to the first factor). Then it does the same again, and again, etc.<\/p>\n

The report of these factors then lists where the questions sit on these ‘factors’. The investigators look at the questions, and start to think “OOOOH all those questions in factor 1 are about breathing difficulty – let’s call that Domain Breathlessness” and so on. (Those name bits are clearly not from the stats machine but from the brains of the investigators.)<\/p>\n

(There are a few marginally different flavours of this, including\u00a0Principal Component Analysis or Canonical Correlation Analysis)<\/p>\n","protected":false},"excerpt":{"rendered":"

It’s another one of those things that you’ll see in a paper, often followed by the word “eigenvalue” and shudder, perhaps externally as well as internally. The’ll be a follow-up of ‘structure’ or the like after that, often fancifully named as different domains. The easiest (!) way to think of how it works is to […]<\/p>\n

Read More…<\/a><\/p>\n","protected":false},"author":7,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2676],"tags":[],"class_list":["post-1215","post","type-post","status-publish","format-standard","hentry","category-stats"],"yoast_head":"\nStatsMiniBlog: Factor Analysis - ADC Online Blog<\/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:\/\/blogs.bmj.com\/adc\/2016\/01\/05\/statsminiblog-factor-analysis\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"StatsMiniBlog: Factor Analysis - ADC Online Blog\" \/>\n<meta property=\"og:description\" content=\"It’s another one of those things that you’ll see in a paper, often followed by the word “eigenvalue” and shudder, perhaps externally as well as internally. 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