Question

If the probability of an event happening is x, what is the probability of the event not happening?

Answer 1

the opposite of a probability happening is its complement, namely 1-P.

so if P(A) = x, then the chance of NOT P(A) is 1 - x.

where "x" is a decimal.

for example if x = 0.3, then its complement is 1 - 0.3 or 0.7.