Abstract
We propose a method that involves quantities independent of strong interaction phases to test the factorization model in Cabibbo-favored two-body decays of D mesons. The method tests if the factorization model correctly predicts the magnitudes of the isospin amplitudes. We have applied this method to the Cabibbo-favored decays DK¯π, K¯ρ, and K¯*π. The test, used as a diagnostic tool, allows us to pinpoint the isospin amplitudes for which the factorization model fails. We discuss the roles of annihilation terms and inelastic final state interactions in resolving the differences between the factorization model predictions and experiments.