Max Value of $P(A \cap B): \min(P(A),P(B))

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In summary, the conversation discusses how to find the largest possible value of the intersection of two events, given that their sum of probabilities is greater than 1. The solution involves rearranging an equation and using the fact that $P(A\cap B)\leq P(A)$.
  • #1
Guest2
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Suppose $A$ and $B$ are events with $P(A)+P(B)>1$. Show that the largest possible value of $P(A \cap B)$ is $ \min(P(A), P(B))$.

I suspect I'm supposed to use $P(A \cap B) = P(A)+P(B) -P(A \cup B)$ but I've no idea how.
 
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  • #2
Rearrange your equation to:
$$P(A)-P(A\cap B)=P(A\cup B)-P(B)$$
I hope you now see that
$$P(A\cap B)\leq P(A)$$
Now finish.
 
  • #3
johng said:
Rearrange your equation to:
$$P(A)-P(A\cap B)=P(A\cup B)-P(B)$$
I hope you now see that
$$P(A\cap B)\leq P(A)$$
Now finish.
Thank you. I get it now. :D
 
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FAQ: Max Value of $P(A \cap B): \min(P(A),P(B))

What does the equation "Max Value of $P(A \cap B): \min(P(A),P(B))" mean?

The equation represents the maximum value of the probability of two events, A and B, occurring together. It is equal to the minimum value between the individual probabilities of A and B.

How is this equation useful in statistics?

This equation is useful in determining the likelihood of two events occurring simultaneously. It helps in calculating joint probabilities and understanding the relationship between two events.

Can you provide an example of how to use this equation?

Sure, let's say we are interested in the probability of both flipping a coin and rolling a dice and getting a heads and an even number, respectively. The equation would be: Max Value of $P(coin=H \cap dice=even): \min(P(coin=H),P(dice=even))

What happens if the probabilities of A and B are equal?

If the probabilities of A and B are equal, the equation simplifies to: Max Value of $P(A \cap B): P(A) = P(B)

Is there a limit to the number of events that can be included in this equation?

No, this equation can be extended to more than two events. For example, for three events A, B, and C, the equation would be: Max Value of $P(A \cap B \cap C): \min(P(A),P(B),P(C))

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