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Show that if P(A)>0, then

P(AB∣A)≥P(AB∣A∪B)

Short Answer

Expert verified

We proved that P(AB∣A)≥P(AB∣A∪B)by applying conditional probability asP(A)>0.

Step by step solution

01

Given Information

IfP(A)>0, We have to prove thatP(AB∣A)≥P(AB∣A∪B).

02

Explanation

AB⊆(A∪B)⇒AB∩(A∪B)=AB

The conditional probability P[AB∣(A∪B)]can be reduced to

P[AB∣(A∪B)]=P[AB∩(A∪B)]P(A∪B)=P(AB)P(A∪B)

Again, from set arithmetic

A⊆A∪B⇒P(A)≤P(A∪B)

Finally

P(AB∣A)=P(AB)P(A)≥P(AB)P(A∪B)=P[AB∣(A∪B)]

03

Final Answer

P(AB∣A)- is the percentage of Athat is in role="math" localid="1647853157806" AB

P[AB∣(A∪B)]- is the percentage of A∪Bthat is in AB.

And since A∪B is larger,P[AB∣(A∪B)]≤P(AB∣A).

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