Proving the Inequalities of Simple Probability: P(A∩B) ≤ P(A) ≤ P(AUB)

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Homework Help Overview

The discussion revolves around proving inequalities related to simple probability, specifically the relationships between the probabilities of events A and B, including their intersection and union.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the relationship between the probabilities of events and their respective sets, with attempts to show that P(A) is less than or equal to P(AUB). Questions arise regarding how to demonstrate that P(A∩B) is less than or equal to P(A).

Discussion Status

Participants are exploring various interpretations of the inequalities and discussing the implications of set relationships on probability. Some guidance has been offered regarding the subset relationships and how they relate to the probabilities, but no consensus has been reached on the proofs themselves.

Contextual Notes

There is an emphasis on understanding the definitions of sets and probabilities, as well as the constraints of working within the interval [0,1] for probabilities. Participants are also navigating the definitions of union and intersection in the context of the problem.

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Homework Statement


Prove the following:

P(A∩B) ≤ P(A) ≤ P(AUB)

Homework Equations





The Attempt at a Solution



I first attempt to show that P(A) is a subset of P(AUB) which therefore means it is ≤ P(AUB):

P(AUB)=P(A)+P(B)-P(A∩B), thus P(A) is a subset of P(AUB)...I think that works...

Any help would be great,

cheers
 
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be careful, probabilities are scalar numbers in the interval [0,1], whilst A & B are sets

so if you can show
A \subseteq B

it follows directly that
P(A) \leq P(B)

as every event in A is also in B
 
lanedance said:
be careful, probabilities are scalar numbers in the interval [0,1], whilst A & B are sets

so if you can show
A \subseteq B

it follows directly that
P(A) \leq P(B)

as every event in A is also in B
So what you're saying is that I have to show that A is a subset of AUB. This is done by definition that AUB=A+B therefore A is a subset of AUB and it follows (as you said) that P(A) is less than or equal to P(AUB). Correct? What would I do to prove the intersection is less than A?

cheers
 
right, and once you have proved one of the inequalities, you could do the other similarly

or P(AUB)=P(A)+P(B)-P(A∩B) yields it directly
 

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