Exponential Distribution for Probability-Probability Plots

The exponential distribution has the probability density function:

f(x) = le[-l(x-q)]

0 <= x < ∞, l > 0, q<x



is the Threshold (location) parameter


is the Scale parameter (an alternative parameterization is Scale parameter l=1/b)


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

Compute from data. When you clear this check box (on the Probability-Probability Plots Advanced tab), you then need to specify the Scale and Threshold parameters (l and q, respectively). When you select the check box and specify the Threshold parameter q, STATISTICA estimates the Scale parameter l from the data.

In general, if the observed points follow the Exponential distribution with the respective parameters, then they will fall onto the straight line in the P-P plot. Note that you can use the Quantile-Quantile plot to obtain the parameter estimates (for the best fitting distribution from a family of distributions) to enter here.