If two candidate materials have very similar diffraction patterns, it may be that PXRD cannot distinguish them, and other techniques must be employed to prove which has been made. When fitting a PXRD pattern, just as when fitting any other data, the most reasonable fit is achieved when the number of fitting parameters is kept as low as possible. In a crystallographic setting, lowering the symmetry of the space group will increase the number of variables in the fit. For this reason, it should be ensured that the improvement of a fit is meaningful when symmetry is lowered. Should the quality of a fit in a high symmetry model be comparable to that of a lower symmetry model, one should pick the former one, again in accordance with Occam's razor.