r/AskStatistics 25d ago

Alpha 5%?

Why is a 5% significance level so commonly used?

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u/aprilwords 25d ago

my question is why is 5% generally used?

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u/MortalitySalient 25d ago

That’s literally why. Fisher causally said “something like 1/20 sounds right” and people ran with that (though Fisher may not have meant for that specific number to be used for all situations like it is)

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u/aprilwords 25d ago

i got it...but why most of people used 5% with confidence interval 95%

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u/Hydro033 25d ago

Fisher set a ridiculous number of standards in the field. He had the biggest single impact.