Statistics
Two independent events
Multiplies the probabilities when the events do not influence each other. For at least one happening, take one minus the product of the complements.
The Formula
P(A and B) = P(A) x P(B)
Multiplies the probabilities when the events do not influence each other. For at least one happening, take one minus the product of the complements.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| P(A) | Probability of A | dimensionless | The first event's probability. |
| P(B) | Probability of B | dimensionless | The second event's probability. |
| both | Joint probability | dimensionless | The chance both events happen. |
What Each Symbol Means
P(A)dimensionless
Probability of A
The first event's probability.
P(B)dimensionless
Probability of B
The second event's probability.
bothdimensionless
Joint probability
The chance both events happen.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate probability page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Probability, filed under Math. Every number the guide produces comes from substituting into this one line.