Abstract
This article proves the truth of the author's I/O Formula for the determination of the number of clerical personnel needed in the parallel-compound-type office. The I/O Formula shows that the mean of the output interval of the clerical unit depends on the larger variable between the mean of the input interval or that of the "service interval" of the clerical unit of the office. This mean of the "service interval" is the mean of the output interval of the clerical unit when the input interval is zero.
