Binomial Random Variables and Probabilities

Binomial Random Variables and Probabilities

Junior College 2

Bernoulli trials

A Bernoulli trial is a random experiment with exactly two possible outcomes: success (usually \(1\)) and failure (usually \(0\)). The success probability is \(p\), and the failure probability is \(1-p\).

Binomial experiments

A binomial experiment satisfies both conditions:

  1. It consists of \(n\) repeated, identically distributed Bernoulli trials, each with success probability \(p\) and failure probability \(1-p\).
  2. The trials are independent, so the outcome of one trial does not affect another.

Binomial random variables

A binomial random variable \(X\) counts the number of successes in \(n\) trials with success probability \(p\).

Notation and support

\[X\sim B(n,p),\qquad X\in\{0,1,2,\ldots,n\}\]

Binomial probability distribution function

BinomPDF

\[P(X=x)=\binom nxp^x(1-p)^{n-x},\qquad x=0,1,2,\ldots,n\]

The binomial coefficient \(\binom nx\) counts the ways to choose the \(x\) successful trials from the \(n\) trials.

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