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# C4 Probability watch

1. Ok, think I must be missing something really obvious here.

Question as follows:

The three events E1, E2 and E3 are defined in the same sample space and P(E1UE2UE3) = 1. The events E1 and E2 are independant. Given that events E1 = 2/3, E2 = 1/4 and E3 = 1/4 find P(E2UE3)

I've worked it out to be 0;
P(E2) + P(E3) - P(E2nE3)
1/4 + 1/4 - 1/16 = 0

But thats wrong, the answer says it is 1/2.

Where is it going wrong. Something to do with 1 & 2 being independant??

Thanks
2. 1 and 2 are indpendent, but it says nothing about 3. Obviously from the answer, it is clear that P(2n3) = 0.

So you must then proceed to prove that the events E2 and E3 must be mutually exclusive..
3. One other thing, 1/4 + 1/4 - 1/16 isn't 0. Not relevant, but just thought I'd say.
4. (Original post by mockelinho)
One other thing, 1/4 + 1/4 - 1/16 isn't 0. Not relevant, but just thought I'd say.

Oh yeah Too much revision, brain must be asleep!!!

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