The four principle assumptions of the simple linear regression model are,
The linearity of the relationship between the dependent variable and the independent variable. That is, value of <em>y, </em>the dependent variable for each value of <em>x</em> the independent variable is, .
Normality of the error distribution. That is, . Thus, the variance of random error e is .
Statistical independence of the errors or specifically no correlation between consecutive errors. That is, if , it implies that.
Homoscedasticity of the errors, i.e. constant variance.
The first assumption clearly indicates that the <em>y</em>-values are statistically dependent upon the <em>x</em>-values.