Probability formula — definition, units and applicable conditions

found 4formulas · currently displayed 4Articles Explanation · Unit · Applicable conditions

Probability

Bayes’ Theorem

P(A\mid B)=\frac{P(B\mid A)P(A)}{P(B)}

updates the probability of an event using observed evidence.

Probability

\mathbb E[X]=\sum_x x\,P(X=x)

averages possible values based on probability weighting. The

Probability

\operatorname{Var}(X)=\mathbb E[X^2]-\mathbb E[X]^2

uses the second-order moment to measure the dispersion of random variables around the mean.

Probability

P(X=k)=\frac{\lambda^k e^{-\lambda}}{k!}

describes the random event count in a fixed window.