# NormalCDF equation

1. Mar 1, 2009

### sollinton

Anyone who has a TI-83 or 84 calculator will probably know about the normalcdf(minimum, maximum, mean, std. deviation) command. It is used to find the area under a normal curve between two given points.

My question is; does anyone know the equation that the calculator uses to find this result? I looked in my Probability and Statistics text book, but could only find the equation for normalpdf:
$$y=\frac{1}{\sigma \sqrt{2\pi}}e^{-\frac{1}{2}(\frac{x-\mu}{\sigma})^2}$$​
If anyone could help me find the equation for normalcdf, I would greatly appreciate it.