statistics
posted by rose .
Use Bayes' theorem to solve this problem. A storeowner purchases stereos from two companies. From Company A, 250 stereos are purchased and 1% are found to be defective. From Company B, 950 stereos are purchased and 10% are found to be defective. Given that a stereo is defective, find the probability that it came from Company A.

number of defective stereos = .01(250) + .1(950
= 2.5 + 95
= 97.5
so prob that the defective one is from A
= 2.5/97.5 = .02564 
I did not know about Bayes Theorem, and just used common sense in my solution.
I looked it up and found this rather confusing description of it
http://en.wikipedia.org/wiki/Bayes%27_theorem
I don't think my old brain feels up to learning more about it, lol