Question 74924
0, 1, -1, 2, 0.0123, 3/5, 5/3
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All are valid probabilities except the following 3:
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-1 is not a probability.  A probability is always a positive value (zero included). It
makes no sense to say that the chances of an event occurring are minus 1 (or minus any number
for that matter.)
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Also 2 is not a probability.  The most the probability of an event occurring can be is 1
which means the event has a 100% probability of happening.  But 2 is greater than 1
so it cannot be a probability.
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Finally, 5/3 is not a probability for the same reason that 2 is not a probability.
It is greater than 1.
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Hope this helps you understand probability a little better.