## Residual Analysis

The standard assumption of regression model is that the random error terms are iid normally distributed random variables with mean 0 and common variance . Thus, the statistical model for the simple linear regression is given by

for
.

The data set consists of

- explanatory variable for 's;
- dependent variable for 's.

*standardized residuals*.

In model validation we look for a pattern, the indication of which suggests that the regression of choice is not a good model.