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The normal, or Gaussian, distribution has a density function that is a symmetrical bell-shaped curve. It is one of the most important distributions in statistics. Use the [normality-assumption] tag for asking about testing for normality.

2 votes

Substracting two normal distributions

If $X$ and $Y$ are independent, we can do $$Var(X-2Y) = Var(X)+Var(2Y)=Var(X)+4 Var(Y) = 1 +4(1) = 5.$$
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