Statistics for Maintenance Modelling: Continuous Lifetime Distributions 1

# The Hazard Function for the Weibull Distribution¤

Hence the hazard function is:

.

I.e. it is just a power of t. If is less than 1, then the hazard rate decreases with age. If = 1, then the hazard rate is constant and the Weibull degenerates into the Poisson/exponential case. If is greater than 1, then the hazard rate increases with age. In particular, if is 2, then the hazard function increases linearly with time. The hazard function against time is shown below with = 2 and = 2, but you can click on the chart for an interactive version in Excel where you can experiment with different values of alpha and beta yourself.

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