Variance, Covariance Matrix, Linear Regression, Standard Error, Confidence Interval.
E(ϵ|X) with 0. Similarly, in the last step, we will substitute E(ϵ_i|X) with 0 for all i in the summation. Doing these two substitutions gets us another important formula for the sum of squares of error terms of a regression model: Formula for the sum of squares of regression errors (Image by