If all the factors in the model are fixed, then the calculation of the F-statistic depends on what the hypothesis test is about, as follows:
If there are random factors in the model, F is constructed using the expected mean square information for each term. For more information, see Neter et al.1.
|Adj MS Term||A measure of the amount of variation that a term explains after accounting for the other terms in the model.|
|MS Error||A measure of the variation that the model does not explain.|
|MS Lack-of-fit||A measure of variation in the response that could be modeled by adding more terms to the model.|
|MS Pure error||A measure of the variation in replicated response data.|
- J. Neter, W. Wasserman and M.H. Kutner (1985). Applied Linear Statistical Models, Second Edition. Irwin, Inc.