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Statistics Question

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Numsgil:
Been working on the mutations probability screen, and I need this information to continue:

There is an Event A

Probability of A = (B or C or D or E)

I know how to modify A if one of B,C,D, or E changes.

I want to know how to modify B,C,D, and E if A changes.  That is, if I want A to be 1/5 of it's original value, how should I change B,C,D and E?

shvarz:
That is not statistics, that is basic arithmetic :)

You need to divide B, C, D and E by 5 as well.

I suspect I did not understand your question.

Numsgil:
Technically it's a probability question.

Remember that Pr(A or B ) = Pr(A) + Pr(B ) - Pr(A * B )

So just dividing everything by 5 won't work.

AZPaul:

--- Quote ---I want to know how to modify B,C,D, and E if A changes. That is, if I want A to be 1/5 of it's original value, how should I change B,C,D and E?
--- End quote ---

I'm assuming B,C,D,E are probabilities of other distinct events.

It is the "or" between B,C,D,E that is the problem. If A changes then there are B*C*D*E solutions to solve for A. What are the constraints on the probabilities of B,C,D,E?   Is B reasonably +- 10% of present value while C can go from 0 to 100?

Good luck on this one!

-P

Numsgil:
B,C,D and E are all user defined, ranging basically from 100% to 0%.  Becauset they are independant, B + C + D + E do not have to add up to be 100%, or 0% or 300% or any other value.

I would like to scale B,C,D and E such that the beginning and end ratios are all the same.  That is, B/C will be the same before and after.

The more I look at the problem, the more I see that this will probably need some thought.

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