Let's say you're looking at statins - a drug used to control cholesterol You want to know whether statins reduce the risk of heart attacks in people who have just been discharged from hospitalpic.twitter.com/tAFz1eGiKr
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So you take a group of people who've been discharged from the hospital. You compare the outcomes for people who filled their prescription for the drug against another group that never got their meds It's a miracle! Statins reduce rates of heart attack by almost 50%!pic.twitter.com/kWBP3IxqpP
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But there's a problem. You see, people who have filled their prescription are different in important ways to people who haven't It's hard to fill your prescription, for example, if you have been readmitted to hospital!pic.twitter.com/cefjFggy9e
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A group of researchers did this exact analysis, comparing different methods of analyzing the data, and they found that if you don't take into account the survival bias you SIGNIFICANTLY overestimate the effectiveness of the drugspic.twitter.com/QX5KpvDawh
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Because you are only looking at survivors - people who stayed out of hospital long enough to fill their prescription - you think that the drug is far more effective than it actually ispic.twitter.com/g8IjjY2CmA
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So what does this mean for twitter and other online experiences? Well, generally speaking, we mostly see 'survivors' being vocal on a topicpic.twitter.com/vbNNzCk69O
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You only see people who have lost a lot of weight promoting certain diets You rarely see people who it didn't work forpic.twitter.com/QlsQLryE0o
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It often feels like there are vast hordes of Flat Earthers, but that's just because the 99.9% of people who looked into Flat Earth and thought "Well this is a crock of faux-intellectual buffoonery" don't go online and rant about their experiencepic.twitter.com/TMwL7YHjEu
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When you feel like everyone online is espousing an absurd fringe belief, remember: chances are you're only seeing the survivorspic.twitter.com/Y6jW0q1d4U
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Replying to @GidMK
I love the classic story of Wald and the WWII bombers, that so nearly describes the bias - and how easy it is to fall victim to it!https://clearthinking.co/survivorship-bias/ …
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I really like that example, thanks!
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Replying to @GidMK
No worries! BTW - that's the same Wald as the Wald chi-square test.
0 replies 0 retweets 2 likesThanks. Twitter will use this to make your timeline better. UndoUndo
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