Homework Statement
For n trials, S_n can be seen as the sum of n independent single trials X_i, i = 1,2,...,n, with \mathbb{E}[X_i]=p and Var[X_i]=p(1-p).2. What I don't understand
I don't understand why Var[X_i]=p(1-p).
We know that: Var[X_i]=\mathbb{E}[(X_i - \mathbb{E}[X_i])^2] =...