ISO 13406-2, A Much More Up-to-date Standard
Apart from the matter of dead pixels, the ISO 13406-2 standard defines flat screen response times as the addition of the full on and the full-off time. If you refer to the text published by the international body, it is the addition of the time needed to display a white dot from black, and vice versa, from black to white. Under this standard, it is not actually the total time that is measured but the time that passes between 10% and 90% of the required brightness. This also corresponds to the definition of "full-on time" in electronics. The problem is that in electronics, the measurement is not considered to be very reliable: It is merely an indication, because it is too dependent upon oscillations at the extremes.
To conceal this defect, the electronics engineers prefer to abandon "full-on time (FT)" in favor of "response time (RT)". A minor point, their RT is not the same as that defined by the ISO. In the former case, they are measuring the time taken to get from 0 to a stabilized state of the system. So theoretically, the response time is the time needed for the transitory state to disappear totally. In practice, the technical people agree that, based on the level of accuracy required, it is the time at the end of which the system response enters a corridor of more or less 5% of the final value without emerging from it. As far as we are concerned, this is once again a measurement of the time needed to get from 0 to 95% or 105%, without any signal being produced during this interval.
If the time measurement adopted becomes that created by the electronics engineers, that would be better, but it's still not good enough.