A subset of the ITER L-mode and H-mode confinement data is tested against the constraints imposed by various theoretical models for thermal plasma transport. Matrix algebra is used to facilitate such tests. A new result obtained is that the fundamental constraint imposed by the high-β collisional Fokker-Planck equation (Kadomtsev) is satisfied by the data. An additional constraint on the characteristic scale length associated with thermal diffusion can also be satisfied by the data. Dimensionally correct empirical scaling laws embodying theoretical constraints can thus be derived.