1. October 4, 2012
Probability
2. Mutually exclusive outcomes
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2. Explanation October 4, 2012
What can happen if you toss a coin?
It can come down heads.
It can come down tails.
These two outcomes are mutually exclusive.
The coin cannot land as both heads and tails.
As the coin must land as either heads, or tails (assuming
it cannot land on its edge!), then the probabilities of
these two mutually exclusive events add up to 1.
P(heads) + P(tails) = 1
Even if the coin were biased towards one side, this
would still be true.
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3. Example October 4, 2012
A bag contains red, blue and green balls.
If you draw out one ball at random, the probability that it
will be red is 3 The probability that it will be blue is 9
14 14
What is the probability that it will be green?
12
P(red) + P(blue) =
14
P(green) = 1 – 12 = 2 = 1
14 14 7
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End