Mark H. answered • 10/18/20
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for any situation with 2 or more possible outcomes, the sum of all the probabilites MUST = 1**.
So, let's define Pno to be the probability of event NOT happening, and Pyes to be the probability of happening.
Pno + Pyes = 1
So: Pyes = 1 - Pno = 1- 55/71 = 16/71
**think about a coin toss. the probability of heads is .5, and .5 for tails. The sum MUST = 1, Read this as the probability of **something** happening......
Mark H.
yes---the coin CAN land on its edge---how about a probability of 0.001 for this? That makes the combined probability for heads OR tails 0.999. That is pretty close to 1.0.....
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10/19/20
David W.
The coin toss is a common illustration of EXACTLY ONE OF TWO POSSIBLE RESULTS. For math and statistics, that is a good assumption. However, there is the very remote possibility that a tossed coin will land perfectly balanced on its edge. (Exhaustive enumeration must consider all physical and theoretical outcomes).10/18/20