Proving p(A|B)=p(A|B'): A Step-By-Step Guide

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    Probability Proof
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Discussion Overview

The discussion revolves around proving the relationship p(A|B') = p(A|B) within the context of probability theory, specifically focusing on the conditions under which this relationship holds, particularly in relation to independent events.

Discussion Character

  • Technical explanation, Debate/contested

Main Points Raised

  • One participant attempts to derive the relationship using the definitions of conditional probability but expresses uncertainty about the validity of their solution.
  • Another participant asserts that the relationship p(A|B') = p(A|B) cannot be proven in general and is only true for independent events.
  • A later reply clarifies that if A and B are independent, then by definition, p(A|B) equals p(A), which implies p(A|B') also equals p(A).

Areas of Agreement / Disagreement

There is a disagreement regarding the generality of the relationship. Some participants agree that it holds under the condition of independence, while the initial claim suggests uncertainty about the proof without that condition.

Contextual Notes

The discussion highlights the dependency on the assumption of independence between events A and B, which is crucial for the relationship to hold. There are also unresolved steps in the initial proof attempt.

chopasticks
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how can i proof that >>>>>> p(A | B') = p(A | B)
well i tried but i think there is a hole in the solution T.T
if we said that
p(A|B)=p(A&B)/p(B)

p(A|B')= p(A&B')/p(b')

= p(A) - p(A&B)/1-p(B)


so0o0o how can i complete it ??
 
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chopasticks said:
how can i proof that >>>>>> p(A | B') = p(A | B)

In general, you can't prove that.

That condition holds ONLY for independent events.

So, in a particular case, you may demonstrate whether that condition holds or not.

If it holds, A and B are independent events, if not, A and B are not independent events.
 
sorry my bad ,, i forgot to mention that A,B are independent
 
In that case, by definition of "independent", P(A|B)= P(A)= P(A|B').
 

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