P-value for kids (well, relatively speaking):
I claim that I make 80% of my free throws.
You say I don't believe you -- you think I make less than 80%.
We go to the gym: I make 8 of 20 free throws.
You say: somebody who really makes 80% would almost never
make as few as 8 out of 20. The data are inconsistent
with your claim.
The P-value is the probability that I would make as few as
8 of 20 if I really make 80% in the long run. This probability
is extremely small, so you have strong evidence that in fact
I make fewer than 80%.
Even without knowing the binomial distr needed for the calculation,
the reasoning is clear. Because software does the calculations, it's
the reasoning that matters.
David
.
.
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