Guido sees the light: PEP 8 updated

[Steven D'Aprano]

On Wed, 20 Apr 2016 01:50 am, Steven D'Aprano wrote:

> - Is the effect due to chance? Remember, with a p-value of 0.05 (the
>   so-called 95% significance level), one in twenty experiments will
>   give a positive result just by chance. A p-value of 0.05 does not
>   mean "these results are proven", it just means "if every single
>   thing about this experiment is perfect, then the chances that these
>   results are due by chance alone is 1 in 20".

Arggh! The above is, of course, *wrong*. This is why statistical
significance is so hard. I know the correct interpretation[1] of p-values
and I still got it wrong.

p-values give the probability of a positive result by chance if the null
hypothesis is true, that is, the chances of getting a false positive
result. "We detected a difference that actually isn't there."

It *doesn't* tell you anything about a false negative result: "We failed to
detect a difference which actually is there." And it certainly doesn't tell
you the chances that the result are true.

More here:

https://www.sciencenews.org/article/odds-are-its-wrong



[1] At least, I'm confident I understand p-values with a 95% significance
level.


-- 
Steven