In: Statistics and Probability
Prove the Following: Where a and b are constants.
a). Σ(?−?̅)=0
b). Var( a + bX) = b2Var(X)
a). We have to prove that
, where a and b are constants.
Now, taking the left-hand side equation and proceeding:

Now, if we take summation inside the bracket, we get:

,
is a
constant term so, summation will change into 

, there
is the total
number of observations

Hence,
Proved.
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NOTE:

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b.) 
Taking the left-hand side equation and proceeding:

we can write it as:

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NOTE:

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NOTE:

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proved.