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## Homework Statement

let [itex]x_{i}[/itex] be a random variable, and let [itex] y_{j} = \sum x_{i}[/itex].

The variance of the random distribution of the [itex]x_{i}'s[/itex] is known, and each y is the sum of an equal amount of [itex]x_{i}'s[/itex], say N of them.

How do I compute the variance of y in terms of [itex] \sigma^2_{x} [/itex] and N?

## Homework Equations

[itex] \sigma^2_{y} = \sum\frac{(y - \mu_{y})^2}{M} [/itex]