The Normal distribution function is determined by the following formula:

f(x) = [1/{(2p)1/2 * s}] * e^[-1/2*{(x-m)/s}2]

-∞ < x < ∞

where

m |
is the mean |

s |
is the standard deviation |

e |
is the base of the natural logarithm, sometimes called Euler's e (2.71...) |

p |
is the constant Pi (3.14...) |

The standardized normal distribution function is used to determine the best fitting distribution.

In general, if the points in the Q-Q plot form a straight line, then the respective family of distributions (Normal distribution) provides a good fit to the data; in that case, the intercept and slope of the fitted line can be interpreted as graphical estimates of the mean (m) and standard deviation (s) parameters, respectively.