Normal Fit

The normal/observed histogram represents the most common graphical test of normality. When you select this fit, a normal curve will be overlaid on the frequency distribution. The normal function fitted to histograms is defined as:
f(x) = NC * step * normal(x, mean, std.dev)
The normal function fitted to cumulative histograms is defined as:
f(x) = NC * inormal(x, mean, std.dev.)
where
NC is the number of cases.
step is the categorization step size
(e.g., the integral categorization step size is 1).
normal is the normal function.
inormal is the integral of the normal function.
See also, Normal Distribution, and Bivariate Normal Distribution.