 The values of these two responses are the same, but their calculated variances are different.In straight line fitting, the model is
where formula_2 is the response variable, formula_3 is the explanatory variable, "εi" is the random error, and formula_4 and formula_5 are parameters.The mean, and predicted, response value for a given explanatory value, "xd", is given by

while the actual response would be

Expressions for the values and variances of formula_8 and formula_9 are given in linear regression.