Binomial Distribution
2 min readDec 5, 2019
Random Variable X has a binomial distribution with parameters (n,p)
Binomial distribution is defined as, where q = 1-p :
- In summary, a sum of independent Bernoulli random variables is a binomial random variable.
Binomial Expectation:
E[x] = np
- proof:
Var[x] = np(1-p)
Moment generating function:
M(t) = (pe^t + (1-p))^n
Bernoulli distribution properties:
- If the random variables X1, X2, …, Xn are n random variables from a Bernoulli trial with parameter p, then X = X1 + X2 + … + Xn has a Binomial distribution with parameters (n,p)
- If X1, X2, …, Xk are independent random variables, and Xi has the binomial distribution with parameters ni and p ( for example X1 ~B(n1,p) . . . , ~B(nk,p)), then X = X1 + X2 + … + Xk has binomial distribution with parameters n = n1 + · · · + nk and p, ~B(n1 + · · · + nk,p).