Supposing that I am able to accomplish the steps just described, let us proceed. I find that straight lines, cubics, quintics, etc., do not provide good fits to the data. The best fits look bad when I view them on the oscilloscope.

The fits of the measured data to the cumulative normal curve are not prohibitively bad. I am more interested in finding a basic function that I can control appropriately with a few perimeters than I am in making contact with any particular theory about the detection process, so I want to find out merely whether anyone in the system has any curve- fitting programs that will accept functions supplied by the user or that happen to have built-in functions roughly like the cumulative normal curve, but assymmetrical.