Help Understanding something basic in probability.

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Discussion Overview

The discussion revolves around understanding the concept of division in probability, particularly the expression A/B. Participants explore various interpretations and contexts in which division may apply within probability theory.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant notes that division of probabilities can be performed like any other numbers, but the result may not always yield a valid probability, referencing likelihood and Bayes' Theorem.
  • Another participant emphasizes the need for specificity in the question, suggesting that division in probability is fundamentally just division, and points to the concept of odds as a possible related topic.
  • A different participant introduces the idea that A/B might refer to conditional probabilities, clarifying that it is not arithmetic division but rather a different concept altogether.
  • Another viewpoint suggests considering division of probabilities as real numbers, linking it to conditional probabilities and Bayesian analysis, while also noting potential complications when dealing with random variables.
  • One participant proposes that the question might be about set difference (A\B), explaining it as a form of subtraction rather than division, and relates it to Venn diagrams.

Areas of Agreement / Disagreement

Participants express differing interpretations of what division represents in probability, with no consensus reached on a singular understanding. Various perspectives highlight the complexity and context-dependent nature of the concept.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the definitions of division and probability, as well as the potential for indeterminate values when dealing with random variables.

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Can somebody explain to be in detail what division represents in probability. Like A/B. I know it sounds very basic, but I just don't understand it. The events and all.
 
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Archive said:
Can somebody explain to be in detail what division represents in probability. Like A/B. I know it sounds very basic, but I just don't understand it. The events and all.

I don't know how much detail you want. You can divide probabilities like any other numbers, but the result will not always be a probability (see likelihood). Formulas where division of probabilities are utilized are so constructed such that if the result is a probability, the values will always be 0< p< 1. (see Bayes Theorem). Beyond this, I can't give you general answer as to what the division of probabilities "represents". It depends on the context.
 
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I think you need to be much more specific with your question. Division is just division, in probability or anything else. Maybe you're referring to http://en.wikipedia.org/wiki/Odds" ?
 
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Welcome to PF!

Hi Archive! Welcome to PF! :wink:
Archive said:
Can somebody explain to be in detail what division represents in probability. Like A/B.

Do you mean A|B?

That's "the probability of A happening, given that B has happened" …

but it isn't division, in fact it isn't arithmetic at all. :smile:
 
I can think of:

1. division of probabilities as real numbers. This is associated with but not confined to conditional probabilities and Bayesian analysis, as noted above.
2. ratio of two random variables. For example you may be asked to derive the distribution of A/B, where each of A and B are random variables. This can be tricky; for example if the domains of both A and B include 0 then with some probability (> 0) the value of A/B will be indeterminate.
 
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Hmmm, if it's not anything that anyone else has already suggested maybe you're referring to the difference (A\B) between sets A and B.

If that's the case, then it's not really division but more like subtraction with A\B being the set of all outcomes in A that are not in B, i.e. A ∖ B = A ∩ Bc (Bc being the complement of B). So if you were drawing out a Venn diagram of that, A \ B would be everything in the A circle except for where the A circle intersects the B circle.
 
I got it thanks guys, sorry for the vague question.
 

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