In handling large quantities of freight the different orders cover many diverse kinds of material, and the jobs vary from one package up to many thousands of packages on one order. The pieces or packages referred to here may be anything from a single casting weighing 20 tons to a shipment of canned goods with 5,000 boxes or cases on a single shipping order. In the long run, however, the different classes of goods could be averaged, and it will be found that in any one locality there would be but shght

FREQUENCY CURVES 185

change from year to year in the average size or weight of package handled. The average weight of package might happen to be 150 pounds, and, considering a whole year, there would probably be very little change in the average weight from month to month. Thus, for our purpose here, the term "piece" or "package" refers simply to the average package handled in different divisions or departments of the work under consideration.

In order to obtain the data regarding the orders referred to in Fig. 157, Fig. 158 and Fig. 159 the order slips are sorted into different piles according to some definitely thought-out plan by which there would not be too many or too few orders in any one class or size group. A little preliminary trial work in sorting would show the best places to set the class limits for sorting the orders into separate piles. After the orders have been separated into piles, it is a simple matter to count the number of orders in each pile to obtain the data from which curve "D" is plotted. It will be noticed from the shape of the curve that the upper and lower limits for each class are well selected so that there is a fairly uniform decrease in the number of orders in each group as the size of the orders increases.