Random time sampling with self‐observation for library cost studies: Unit costs of interlibrary loans and photocopies at a regional medical library

A simple general method for determining labor costs, random time sampling with self‐observation, is described. Unit costs of providing interlibrary loans and photocopies were determined by this method. The working time of all appropriate library personnel was sampled using Random Alarm Mechanisms and a structured checklist of mutually exclusive tasks. The workers' actual wage rates were applied to the resulting percentages. The total lender's unit cost per request received, including direct labor, materials, fringe benefits, and overhead, was $1.526 for originals mailed postpaid by lender and $1.534 for photocopies mailed. Corresponding unit costs per request filled were: originals $1.932 and photocopies $1.763. Labor costs included the costs of verifying, paging, copying, packaging & mailing, record keeping, and reshelving, based on wage rates in effect February 1969. This practical, objective method of work sampling causes minimal interference with service operations, and does not distort the data being collected. Acceptable reliability can be achieved at low cost. Under comparable conditions, the cost of providing a photocopy did not exceed the cost of lending an original document.