Statistical study of the spot-plate technique for viable-cell counts.

A statistical study of the spot-plate technique was made for the purpose of establishing an acceptable counting range. The organism used in these studies was Micrococcus lysodeikticus. Standard deviations and coefficients of variation were computed for counts ranging from 20 to 440. The lower and upper limits for acceptable counts, based on coefficients of variation of 10 and 5.8, respectively, were chosen as 100 and 300.