# Thread: Ols help urgent

1. ## Ols help urgent

i'm having trouble demonstrate the b) question, if u please help me would be really apreciated:

(this exercise is on the upload photo too)

1. Consider the model
Yi = Xi + ui; i = 1; :::;N
where ui satis…es the usual hypotheses.
(a) Derive by OLS the estimator of the parameter :
(b) Show that the estimador obtained in (a) is unbiased. (Hint: Compute the
expected value of the estimator.)

my resolution is on the anex file, also please tell me the right way to do it the b) correctly.

thanks and sorry for my english.

2. ## Re: Ols help urgent

Hey kengil64.

One thing is that you can't cancel Sigma (x_i*y_i) / Sigma(x_i^2) the way you did it: you have to leave it like that. Cancelling terms like you do with normal fractions is not the same when you have summations.

You can only cancel things that are common terms outside any summation or multiplication and not inside (and if it's inside you have to show it's independent of the terms in the summation or multiplication and can be brought out).