补集概率计算器
计算事件不发生的概率，即补集概率。
P(Not Event)
0.650000
P(Not Event) vs P(Event)
公式
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.
计算示例
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
常见问题
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.
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