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Bayes' rule: Odds form

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[-]Mark Hamilton3y*10

I don't know if this is helpful or not, but, as someone who is genuinely trying to use this to learn Bayes' theorem and doesn't already understand it, I found the following confusing:

When you introduce P(X) you don't explicitly show how those cash out. I eventually figured out the proper way to do it after reading the whole page, but I was a bit confused. Just something simple like "P(sick)=.2". Maybe that seems obvious, but it wasn't until I tried to do the example equations on my own that I realized I wasn't actually sure how "P(X)" translated into numbers in an equation.

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[-]Conor Duggan4y*10

Full what?

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[-]Philipp Cannons5y*10

Why does P(Y) become P(H_j)/P(H_k)?

Does this imply Y = [H_j, H_k]?

So far P(Y) referred to P(sick) whereas now it refers to P(sick)/P(healthy).

This is confusing me.

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[-]Dewi Morgan7y*30

Is this a probability or an odd? What's a "chance"? In this list, "chance"s are expressed both as a fraction, and as a percentage, like some kind of hybrid probablodd. This feels like muddying the waters. When you're introducing a new concept like "probability and odds, while synonyms in lay speak, are different things in statistics", it's probably not good to conflate both with another lay synonym like "chance".

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[-]Dewi Morgan7y*30

In this page, the terms "probability" and "odds" are used in the statistical sense of "In the classical and canonical representation of probability, 0 expresses absolute incredulity, and 1 expresses absolute credulity." (from the linked definition) and "odds are a ratio of desired outcomes vs the field" (has no linked definition, I'm just wildly guessing based on context).

Explaining this distinction clearly at the outset for non-statistically trained users, may be worthwhile.

Explaining what is meant by odds, on this page about them, may be worthwhile.

It may also be confusing to a new reader, who has just read a linked definition which explains that probabilities are expressed as a number from 0 to 1, to see it expressed in the very same paragraph (and elsewhere on the page) as a percentage instead. I feel that this is a lack in the definition, though, rather than a problematic inconsistency on the page: I find the expression both as 0-1 and 0%-100% meant I looked at the problem from both points of view, and so felt it had a firmer grasp on the concepts.

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[-]ubs izo8y*10

I'd really like to see links to problems or sums at each level, i feel like a single or two worked out examples is not enough, and that say ten problems that help one think this idea and connected ideas through would be great.

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[-]yassine chaouche8y*20

Would that mean that the strength of evidence is the TP/FP ratio ? in that case, it would have the same definition as the relative likelihood. Wouldn't there be a better definition for either one of the notions so that we can easily differentiate them ?

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[-]Haakon Borch8y*40

It was unclear when reading this which test "this test" referred to. I ended up figuring out the false negatives and true positives of the 60/20 test instead of the 90/30 test and was subsequently confused because 1:2 != 1:7. This might be an issue with my reading comprehension, but I figured I should mention it anyway.

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[-]Stephanie Koo8y*10

Just reiterating that it's 18% of all students (sick and healthy). That's because it's a 90% (0.9) chance the blackened tongue depressor belonged to a sick student, out of all the sick students (20% of total student population).

Sorry if this is really obvious to others, it just took me a while.

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[-]Martin Bishop8y*150

This confused me at first because I didn't realize it was sarcasm and I thought I was missing something. "Is there any reason why distinguishing between assumption and proposition is a bad idea?"

Reply14
[-]Anareth A9y*10

“got” would be clearer.

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[-]Anareth A9y*10

The following would be simpler and more consistent with the beginning of the sentence: “the fraction of sick patients that got a positive result”

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[-]alexei9y*10

test

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[-]Tom Voltz9y*10

I seem to have broken the display by proposing an edit! The meta-level script is showing in some places. I hope that doesn't cause unneeded headaches.

I only wanted to emphasize the difference in notation between a horizontal line ("---", as in relative probabilities) vs. a forward slash ("/", as in probability that something will occur). I could find no misuse of the notation when I re-read the page, but it was a bit confusing for me jumping in at the stage I did (is there an earlier page briefly defining various notation?), since I am accustomed to both these symbols meaning "divided by", which lead me to instinctively calculate a percentage or fraction whenever I see one or the other. This could be an idiosyncrasy of an engineering workplace.

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[-]Emile Kroeger9y*20

This page asks me if I learnt the concept of "Odds ratio" - but nowhere in the page does it actually explicitly talk about odds ratios, only about odds.

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[-]Eric Rogstad10y*70

Which calculation?

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