Statistical analysis of particle size data is limited when one uses sieve-derived weight frequency data, inasmuch as there is no well-defined sample 'size' associated with the total sample. However, the smallest measurable (reproducible) weight-unit used in the technique may be considered as a basic unit for weight frequency. On this basis, the sample size is defined by the total number of such weight units in the sample. Thus, if the sieve fractions are weighed to the nearest 0.05 gram, the sample size is found by dividing the total sample weight by 0.05 gram. A numerical example lends support to the concept that the population units may be advantageously defined as aggregates of grains, rather than as individual grains, in size frequency analysis.