Conditional Probability

What is the Chance of Rain: Local vs Federal Forecasts

The local weather forecaster says “no rain” and his record is 2/3 accuracy of prediction. But the Federal Meteorological Service predicts rain and their record is 3/4. With no other data available, what is the chance of rain?

A.   3/5 C.   1/6
B.   1/4 D.   5/12



For outcomes that are equally likely to occur:

$P = \dfrac{\text{Number of favorable outcomes}}{\text{Total number of possible outcomes}}$


If the probability of an event to happen is p and the probability for it to fail is q, then

$p + q = 1$


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