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Let x1, x2 x3 ....be a sequence of independent and identically distributed random variables, each having...

Let x1, x2 x3 ....be a sequence of independent and identically distributed random variables, each having finite mean E[xi] and variance Var（xi）.
a）calculate the var （x1+x2）
b）calculate the var（E[xi]）
c） if n-> infinite, what is Var（E[xi]）？
Math   Statistics-And-Probability   
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