I'm having a bit of trouble understanding probability.
So I came across this data with a question:
The question is:
"Calculate the probability that a randomly selected shareholder owns fewer than 200 shares or is against the merger."
Now I thought that I could just add the 12,3,10 and 6 together to get 31, therefore the probability would be 31/50.
I then decided that since I knew the answer I would try using the formula: "p(a)+p(b)-p(a∩b)" to get the same answer, however, this was not the case. Instead, I ended up getting 19/50+15/50 - (19/50x15/50) = 283/500
Obviously, these are different answers so... Which one is correct and where did I go wrong with the other?
(Also, sorry for making this so long, I wanted this to be fairly detailed so you could see my steps and thought process)
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- 16-10-2016 05:21
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- 16-10-2016 06:40
The problem with the second method is the working out of P(A and B). P(A and B) = P(A) x P(B) is only true for independent events.