A Weibull failure distribution is often used to characterize failure times in reliability models. It has two parameters: a Slope and a Mean Lifetime. The slope is dimensionless and the mean lifetime has dimensions An output attribute for an element that defines the dimensionality (in terms of Length, Time and other fundamental dimensions) of the output. of time. The slope controls the shape of the distribution. A slope of 1 produces an exponential curve; a slope of 3.3 produces a normal distribution; slopes between 1 and 3.3 produce normal-like curves with a trailing tail (see below); slopes greater than 3.3 produce normal-like curves with a leading tail.
The curve below shows a Weibull distribution that has been delayed by 10 years:
Note: The Slope and Mean Lifetime should not be specified as functions of time. If they are, only the initial values will be used.