An expression for the effective collision frequency is derived in terms of⟨E2⟩/4&pgr;n&kgr;Te. This quantity is shown by similarity considerations to be the same in many different situations. From its value 0.07, and even from values down to(me | mi)2, it is concluded that present quasilinear theory and nonlinear wave equations cannot be used to explain the experimental results. The value 0.07 can be understood as the equipartition between the kinetic energy of the trapped particles and the energy in the electric fields.