DISTRIBUTION OF REPAIR COSTS
A simulation procedure is used to determine which of the rules of thumb provides the lowest average cost over time. The most unpredictable farm tractor cost is repairs. Before simulation can take place, a distribution must be constructed from which yearly repair costs can be drawn at random. Because repair costs fluctuate widely, collection of a large number of observations is necessary to determine with some degree of confidence the distribution's shape. Data collection poses a problem since it is difficult to obtain data from a large number of tractors which are the same age, size, and which are used the same amount. This problem was overcome by constructing a generalized distribution. Repair cost data were collected on tractors of various sizes, ages, and use levels. Given the size, age, and use, a repair cost equation was used to