An analysis of the accuracy of estimating and the distribution of tenders

This paper is a statistical analysis of the distribution of tenders and how it can be derived from the distribution of estimators' cost rates. It derives equations to explain the distribution of unit and elemental rates which are found to depend on the contribution of the task to the total cost, labour content and procurement method. It further demonstrates that while there is considerable co-variance between unit rates, there is no such interdependence between either elemental or subcontractor rates. This means that the central limit theorem can be used to forecast the distribution of tenders.