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- Apr 14, 2013

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The random variables $X_1, X_2, \ldots , X_{10}$ are independent and have the same distribution function and each of them gets exactly the values $\pm 2$ and with equal probability.

We define the random variable $S=X_1+X_2+\ldots +X_{10}$.

I want to calculate $\mathbb{E}(S^2)$.

Could you give me a hint how we could calculate that? I don't really have an idea.