Question

if the probability of an event happening is 0.45. what is the probability of the event not happening?

Explanation:

Step1: Recall probability rule

The sum of the probability of an event happening and not - happening is 1. Let $P(A)$ be the probability of the event happening and $P(\overline{A})$ be the probability of the event not - happening. So $P(A)+P(\overline{A}) = 1$.

Step2: Solve for $P(\overline{A})$

We know $P(A)=0.45$. Then $P(\overline{A})=1 - P(A)$. Substitute $P(A) = 0.45$ into the formula: $P(\overline{A})=1 - 0.45$.
$P(\overline{A})=0.55$

Answer:

$0.55$