ASM 29.5

[Old_Timer]

The solution states that the mean of fitted Y = the mean of Y. Is that always true? I don't recall seeing that result earlier.

Thanks for your help!

[Abraham Weishaus]

For a model with a constant, the constant is set in such a way as to make this equality true. For example, in the 2 variable model, alpha hat is Y: bar minus beta hat X bar, so the mean of the fitteds (alpha hat plus beta hat times X bar) equals the mean of the actuals (Y bar).

The statement is not generally true for a model without a constant.

[Old_Timer]

Thanks!