Density Function. The Weibull distribution has the probability density function:

f(x) = c/b*(x/b)(c-1) * e[-(x/b)^c], for 0 <= x < ∞, b > 0, c > 0

where

b |
is the scale parameter |

c |
is the shape parameter |

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

Distribution Function. The cumulative distribution function (the term was first introduced by Wilks, 1943) for the Weibull distribution is:

F(x) = 1 - e[-(x/b)^c]

W. This field displays the current variate value for the Weibull distribution. When you edit this value (either manually or with the microscrolls), Statistica computes the associated p-value for the specified parameters.

p. This field displays the p-value computed from the specified variate value and parameters or you can enter a desired p-value (either manually or edit the existing value with the microscrolls) and compute the critical value of the distribution for the specified parameters.

Scale, Shape. Specify here the scale and shape parameters of the distribution, b and c, respectively. If one or both of these parameters are changed, the p-value is recomputed based on the respective variate value.