The prediction is (not false) if (no quakes fit the window).

IFZ (no quakes fit the window) THEN prediction = FALSE

IFZ hitcount = 0 THEN hit = FALSE

which is logically the same as:

IF hitcount != 0 THEN hit = TRUE

I was trying to show the inverse of the logic as a way of showing that more than one quake fitting a prediction is no different than only one quake fitting the prediction - ie it does not score any differently.

I might be a little more familiar with Boolean logic because of my electronics background. All digital electronics are made up of logic gates - AND, OR, NOR, NAND, NOT, XOR. Had a lot of fun in class turning truth tables into digital circuit designs.

Brian