A comparison of a systematic sampling method with complete random sampling for estimating total numbers of nerve fibers

This paper considers the sampling precision of a systematic sampling method for estimating total number of nerve fibers exposed on cross section of a nerve trunk. The mean square error (MSE) associated with systematically selecting every Kth grid square (traversing the section in a serpentine pattern) was determined in each of nine nerve fiber populations and compared to the MSE obtained using a completely random selection of grid squares. For both sampling methods sampling errors of approximately 10% could be achieved by counting in 10% (K = 10) of the available grid squares. To reduce the MSE to 5% or less necessitated, for both methods, counting approximately 50% (K = 2) of the cross sectional area. Although the results of this investigation are based on the study of but one class of nerve fiber population (cervical sympathetic nerve trunks), the authors believe that certain of the results will have practical application in similar quantitative studies. More important, it is hoped that this study will motivate further investigations into the precision of sampling methods currently employed (and others which may be proposed) in the quantitative study of the nervous system.