# Math Help - Help with Regression Modelling Assigment

1. ## Help with Regression Modelling Assigment

Consider the linear model $Y_i = B_0 + B_1X_i + e_i ;\ i = 1,....,n$

where $e_i$ are assumed to be i.i.d. $N(0,stder)$ distribution, where $stder$ represents the standard error.

<usual notation for a normaly distributed RV would be ~N(mean,variance) >

For the LS estimators $b_0$ and $b_1$ of $B_0$ and $B_1$ show that

a) $cov(b_0,b_1) = -(stder)^2(\bar{X}/S_{xx}).$

b) $cov(\bar{Y},b_1) = 0$. That is $\bar{Y}$ (the mean of $Y$) and $b_1$ are uncorrelated.

PS: I wanted to put the above in Latex by putting my math stuff between (math)....(/math) (but with square brackets) like the Latex tutorial suggested, however there seems to be something wrong with that key on my keyboard. Is there another way to do it?