In y electronics and electricity class, we did a lot of work with electricity, and one of the things we measured was that different people have much different internal resistances. The same voltage will lay someone out, while their partner could take it and barely even notice. I guess it goes the same as anything else, some people go down with one shot, and in a recent CCW class, the teacher told of a guy that took over 100 rounds and was still coming. I dont know how valid that story is, but it illustrates the point.
I know what test you are talking abuot.. I did the same thing. It actually measures the resistance of your skin.
I can't imagine tasers being effective at all, since there is no current in them at all, and current is what will do damage, not voltage.