Other Indices of Fit - Bollen's Rho

This comparative fit index computes the relative reduction in the discrepancy function per degree of freedom when moving from the "Null Model" to the k'th model. It is computed as:

(129)

 = degrees of freedom for the "Null Model"

 = degrees of freedom for the k'th model

 = the discrepancy function for the "Null Model"

 = the discrepancy function for the k'th model

Comparing Equations 129 and 126, we see that, for even moderate N, there is bound to be virtually no difference between Bollen's Rho and the Bentler-Bonnet Non-normed fit index.