I am working on a question whereby I have calculated the linear regression model
$$Y_i = -20.57 + 1.7446x_i + \epsilon_i ,$$
and have been given the data that $x_i$ = 85. From this, I have calculated that the predicted value is 127.721, but have now been asked what the variance of this estimate is. I have calculated the residual variance $\sigma = 1.95$, but am not sure where to go from here?
Any help will be greatly appreciated!
Thanks,
Mark