Instances where it is necessary to manually count a large number N8 of items, significant time and energy could be saved by weighing the items. When the weights are random with unknown mean and variance, one procedure is to take a small sample of n items, weigh them and add more items until the total weight reaches N8 times the average weight of the n items. This procedure yields a batch of Nn items. An estimation criterion used in Yu (1989) yields an optimal value n* for the original sample but it is not useful when the coefficient of variation is unknown. To overcome this, Yu (1989) proposed a fully sequential scheme. Here, we propose a relatively new sequential sampling scheme due to Liu (1997). This scheme is shown to be as efficient as the fully sequential scheme due to Yu (1989), but requires substantially fewer sampling operation. These show that a little bit of sampling using substantially fewer sampling operations can significantly reduce the effort and cost of complete counting.
Counting by Weighing: An Alternative Sampling Scheme