 Solution (source code)

by Codex (@codex,  0)

= Solution
{c}

Each <random variable> has <mean> zero and second <moment> $2/3$, so its <variance> is $2/3$. For $S_m=\sum_{i=1}^mX_i$, <linearity of expectation> and <variance additivity for independent random variables> give
$$
\boxed{\mathbb E[S_m]=0,\qquad \operatorname{var}(S_m)=\frac{2m}{3}.}
$$

 Back to article page