P-value

https://arbital.com/p/p_value

by Stephen Fox Jan 2 2020 updated Jan 2 2020

The probability of observing the sample data we have _actually_ observed; the sauce behind significance testing.


[A] p-value is the probability of our observing the sample data we have observed when, in fact, the two population averages are identical.

An Intuitive Explanation

Imagine you are comparing two observations (a la some difference of means test): the mean and standard deviation of employment rate in California and New York, USA.

You can think of the p-value as the probability that the apparent difference in employment rate between California and New York is due to random chance.

Think about this:

Closely related to this idea is [statistically_significant statistical significance], where a p-value of 0.05 is typical and 0.01 is used in more stringent trial.

[todo: Mathematical explanation]

[todo: link into a statistics learning path]

[todo: equation from mean-value test]