**Block Category:** Random Generator

**Description:** The weibull block generates random
numbers from a Weibull distribution. The Weibull distribution is often used in
the field of life data analysis due to its flexibility—it can mimic the behavior
of other statistical distributions such as the normal and the exponential. If
the failure
rate decreases over time, then *k* < 1. If the failure
rate is constant over time, then *k* = 1. If the failure
rate increases over time, then *k* > 1.

An understanding of the failure rate may provide insight into the cause of the failures:

• A decreasing failure rate would suggest infant mortality. That is, defective items fail early and the failure rate decreases over time as they fall out of the population.

• A constant failure rate suggests that items are failing from random events.

• An increasing failure rate suggests wear out. That is, parts are more likely to fail as time goes on.

When *k* = 3.4, then the Weibull distribution appears
similar to the normal
distribution. When *k* = 1, then the Weibull distribution
reduces to the exponential
distribution. For more information, see http://en.wikipedia.org/wiki/Weibull_distribution.

**Alpha:** Specifies the shape of the curve. You can
enter a value in hexadecimal notation or
as a C expression.

**Lambda:** Specifies the scale of the curve. As you
increase the value of Lambda, curve is stretched. You can enter a value in hexadecimal
notation or as a C
expression.

**Label:** Indicates a
user-defined block label
that appears when **View > Block Labels** is activated.