Complement Probability Calculator
Calculate the probability that an event does NOT occur, which is 1 minus the probability of the event.
P(Not Event)
0.650000
P(Not Event) vs P(Event)
Formula
## How to Calculate Complement Probability ### Formula **P(A') = 1 - P(A)** The complement of an event A includes all outcomes where A does not happen. Since all probabilities must sum to 1, the complement is simply 1 minus the event probability. This is often useful for "at least one" problems where computing the direct probability is complex.
Esempio Risolto
The probability of rain is 0.35. What is the probability it does not rain?
- 01P(rain) = 0.35
- 02P(no rain) = 1 - 0.35 = 0.65
- 03As a percentage: 65%
- 04Odds against rain: 0.65 / 0.35 ≈ 1.857
Domande Frequenti
When is the complement rule most useful?
It is especially handy for "at least one" problems. Instead of computing P(at least one) directly, compute P(none) and subtract from 1.
Can the complement probability be zero?
Yes. If P(A) = 1 (the event is certain), then P(not A) = 0. Conversely, if P(A) = 0, then P(not A) = 1.
How does the complement relate to odds?
Odds against = P(not A) / P(A). Odds in favor = P(A) / P(not A). These are reciprocals of each other.
Impara