This page provides more detailed information on the statistical models used in InfoAsset Planner's Deterioration Models.
Cohort Model: Weibull
Data Inputs: User-defined life expectancies (per Cohort), or failure Data.
Processes: Estimates input parameters (typically referred to as the shaping factors) for the Weibull distribution and then calculates the probability (for a given Cohort) as a function of time.
f(t) is pipe failure probability density function (pdf);
t is the pipe age;
k is the shape parameter;
λ is the scale parameter;
c is the resistance time or the elapsed time from the construction to the first observed failure (t > c).
Outputs: Failure Probability Density, Cumulative Failure Probability, Survival Probability, Residual Life Expectancy
Comments: Network and Cohort level analysis, more general failure equation designed for deterioration analysis for many different applications, easier to converge and generally requires less data