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>"That number is meaningless without knowing how likely it is for people who don't drink it to develop cancer, which is about 40%. That's the p-value, and it gi
by nonbel 11y ago
>"That number is meaningless without knowing how likely it is for people who don't drink it to develop cancer, which is about 40%. That's the p-value, and it gives you a starting point for developing an experiment."
That is the frequency of cancer given not drinking fluoridated water. That is not a p-value.
- ewzimm 11y agoSorry, I saw how that could be misleading by saying that's so I clarified right away... not fast enough I see. I mean that comparing the observed data to a baseline gives you a p-value.
- nonbel 11y agoThis example is still misleading because you have selected a special case where the frequencies are exactly equal. In any other case the p value will depend on the sample size.
- ewzimm 11y agoTrue, but what I'm trying to convey is that if someone just wants to generally understand what a p-value is from no knowledge, understanding how to read a specific number isn't important. At first, I wasn't even going to include a specific number, but I realized not having one would be confusing in its own way. Looking at a specific p-value and understanding its significance is only useful once they're actually looking at a study. But first they just want to know how it's derived and what it's good for.