Parameter estimates for Probit Analysis

The probit model links the stress level to the failure probability through the chosen cumulative distribution function. The probit model can be expressed in terms of the shape and scale (Weibull distribution) or location and scale (all other distributions) of the chosen distribution. For the normal distribution, the location parameter equals the mean and the scale parameter equals the standard deviation.

The probability of unit failing at a given stress level can be restated as the probability that a unit's tolerance is less than a given stress level. The distribution of these probabilities is known as the tolerance distribution.