Let us suppose that I interrogate the various files, or perhaps interrogate a master-integrated, network file, and find out that no such programs exist. I decide, therefore, to go along with the normal curve.
At this point, I have to do some programming. I want to hold on to my data, to the programs for normal curve fitting, and to display programs that I borrowed. What I want to do is to fit cumulative normal curves to my various sub-sets of data constraining the mean and the variance to change slowly as I proceed along any of the ordinal or ratio- scale dimensions of my experiment, and permitting slighly different sets of perimeters for the various subjects.