In: Statistics and Probability
(estimate) is
an unbiased estimator of
.
Proof: = E(
^)=
E(
Ci yi)
=
Ci E(yi)
=
Ci(
o +
1Xi)
=
o
Ci +
1
CiXi equation
1
Now
Ci=
=
= 1
= 0
Substituting values of 
and
in
equation 1
E(
o^)=
o
Hence
o^ is an unbiased
estimator of
o.
Var(
o^)= Var(
)
=
=
=
=
)
=
Note that
Var(
o^)
= 
Hence the result.