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Home Multivariate Data Basic Knowledge Selection of Variables Mallows Cp Statistic
See also: variable selection, Data Set - Gasoline Samples 

Mallows Cp Statistic

C.L. Mallows developed a method to find adequate models by plotting a special statistic against the number of variables+1.

Cp = SSres/MSres - N + 2p,

where
  SSres is the residual sum of squares for the model with p-1 variables,
  MSres is the residual mean square when using all available variables,
  N is the number of observations, and
  p is the number of variables used for the model plus one.

The general procedure to find an adequate model by means of the Cp statistic is to calculate Cp for all possible combinations of variables and the Cp values against p. The model with the lowest Cp value approximately equal to p is the most "adequate" model.


Home Multivariate Data Basic Knowledge Selection of Variables Mallows Cp Statistic