Then a rule might be to purchase 17 percent more valves than the number of valves counted on the engineering drawings. Suppose that someone tabulates the number of valves used on a substantial set of previous similar projects and finds that, in every case, the number of valves actually installed was always 1.17 times the number of valves counted on the engineering drawings by the quantity surveyor.
Accounting for Random Error Versus Systematic ErrorĪn example may help in illustrating the point.
