##### Basic stats question using multiplication rules

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I'm just learning stats. A little confusing. Here s the question:

Out of 100 people, 14 are Rh- (blood type), 40 are type A, and 5 are universal donors (Rh- and type A). If 4 of the 100 subjects are randomly deleted, find the probability that they are all universal donors. A) assume selections are made with replacement B) assume selections are made w/o replacement.

How to do this with P(A & B)=P(A) x P(B) ?

I know how to find the probability of selecting one universal donor, but not four times.

Apr 26th, 2015

This would be done the same way; the probability of 4 of the universal donors being deleted is 5/100x4/99x3/98x2/97. Each scenario would be viewed independently.

Apr 26th, 2015

Oops, meant to write "randomly selected", but I don't think that changes anything.

Apr 26th, 2015

It should be the same.

Apr 26th, 2015

And my first response is for without replacement; if it was with replacement, then it would just be 5/100^4

Apr 26th, 2015

Wow, thanks. I just found this site. Pretty amazing. Thanks so much for your help!

Apr 26th, 2015

Not a problem!

Apr 26th, 2015

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Apr 26th, 2015
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Apr 26th, 2015
Oct 18th, 2017
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