S. Nokoe et C. Agbavwe, DETERMINING THE OPTIMUM NUMBER OF STRATA FOR SAMPLING A NORMALLY DISTRIBUTED FOREST POPULATION, Discovery and innovation, 5(4), 1993, pp. 301-305
The purpose of the study was to determine the optimum number of strata
(L) in a forest population when the underlying distribution is normal
, and the variable for stratification is either the variable of intere
st or a linearly related auxiliary variable. The technique used in bot
h cases involved the combination of the Neyman allocation of strata sa
mple sizes, Dalenius and Hodges' cumulative square root frequency meth
od, and a simple cost function of the form suggested by Dalenius. Our
results showed that for a normally distributed diameter at breast heig
ht (dbh) and total height, eight strata, were about optimum. Gains in
efficiency over the unstratified situation were 1500% for dbh and 2500
% for total height. These optimal values represented those values for
which further increases in L did not produce appreciable decrease in e
stimated variance of the mean of the variable of interest.