Weibull Distribution

The Weibull distribution is the standard choice for time to failure and reliability work. Its shape parameter lets it represent parts that fail more often as they age, at a steady rate, or early in life.

Write Weibull(shape, scale):

Weibull(2, 5)

A shape above 1 means the failure rate rises over time (wear-out); a shape of 1 is a steady rate, the same as the exponential; below 1 means early-life failures. The scale stretches the distribution along the time axis. Use it for equipment lifetimes and maintenance intervals.