Is it no Longer Necessary to Test Cosmologies with Type Ia Supernovae?

We look at the current practice of analyzing the magnitude–redshift relation from the data on Type Ia supernovae. We show that, if the main aim of such analysis were to check the validity of a cosmological model, then the recently advanced arguments do not serve the purpose. Rather, the procedure followed tells us only about the statistical significance of the internal parameters used in the model, whereas the model itself is tacitly assumed to give a good fit to the data. A statistical assessment of the procedure is given and it is argued that given the growing data, the validity of the cosmological model should be checked first rather than the spread of any internal parameters. In passing we also discuss some aspects of the Milne model in the light of the present test.