A useful general distribution for describing failure time data is the Weibull distribution named after the Swedish professor Waloddi Weibull (1887-1979), who demonstrated the appropriateness of this distribution for modeling a wide variety of different data sets.It is often meaningful to consider the function that describes the probability of failure during a very small time increment (assuming that no failures have occurred prior to that time). This function is called the hazard function (or, sometimes, also the conditional failure, intensity, or force of mortality function), and is generally defined as:
RAM Commander Weibull Module
RAM Commander reliability software provides Weibull module allowing input/import of failure statistics (time to failure) and calculation of Weibull distribution parameters (Shape and Scale):
Weibull parameters calculation algorithm takes into consideration “censored” data too, e.g. not only failures but also times at which equipment was tested and appeared to be operational.After the calulation user may generate Weibull reports and graphs like PDF (Probability Density Function), CDF (Cumulative Distribution Function), FR(t), number of failures till time t etc. to predict failures, plan warranty times etc.:
Distribution parameters can be used in system reliability analysis using Reliability Block Diagrams module of RAM Commander.