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P(X=k)=pk(1−p)1−kP(X = k) = p^{k} (1-p)^{1-k}P(X=k)=pk(1−p)1−k

pkp^{k}pk

,

(1−p)1−k(1-p)^{1-k}(1−p)1−k

Bernoulli Distribution PMF

Click on formula components below to explore their properties

Full Formula Properties

Category: Probability Theory

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Baby Fast Definition

This formula gives the chance of getting a 1 or 0 in a single coin‑flip‑like experiment, using the coin's bias p.

The Bernoulli PMF tells us how likely a single yes‑or‑no experiment is to result in success (1) or failure (0). It combines a factor that rewards success with one that rewards failure, guaranteeing the probabilities always add up to 1 across the two possible outcomes.

Role:

Computes the probability of observing a specific outcome (0 or 1) in a Bernoulli trial

Domain:

k∈{0,1}, p∈[0,1] (input: trial outcome and success probability; output: probability value)

Binding:

Multiplies the success term p^{k} with the failure term (1-p)^{1-k}, linking outcome and probability

Variance:

Changes with both k and p; probability shifts from p to 1‑p as the outcome flips

Geometric:

Can be visualized as the area of a rectangle whose side lengths are the two term values

Invariant:

The exponents always sum to 1 (k+(1‑k)=1), ensuring the expression stays a proper probability

Limits:

If p→0, probability →0 for k=1 and →1 for k=0; if p→1, the opposite holds

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