Asro Pun' Blog

Updating the Lang Factor and Testing its Accuracy, Reliability and Precision as a Stochastic Cost Estimating Method

Posted by asro on 8 May 2015

The Lang factor is a one of the factored estimating techniques that is recommended by AACE International for class 4 and class 5 estimates. This method was proposed by Hans J. Lang in 1940’s use a simple formula: consist of a set of factor multiplied by the Total Equipment Cost (TEC) to obtain the Total Plant Cost (TPC). These factors are 3.10 for solid plant, 3.63 for solid-fluids plant and 4.74 for fluids plant.

Over the ensuing decades, several people tried to calculate the Lang factor by using their current data.

In this paper, the fluid plant Lang factor is updated and tested its accuracy, precision and reliability by using historical project data from a major Indonesian national oil company.

The result of updating and testing show that while the Lang factor is appropriate for use for Class 4-5 estimates, because it exhibits such a high degree of variability; it is not recommended for creating high accurate, reliable or precise of cost estimates.

Click here to download the paper.


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