An empirical test of sample size and precision of Robin's method of strain analysis

Using Robin's method of strain analysis, we attempted to determine empirically how many inclusions must be measured to obtain principal strain ratios that are reproducible within ± 10%. Six large specimens of deformed leuco-granite with strained lenticular quartz aggregates were studied from a crescentic pluton in the Grenville Province of southeastern Ontario.Between 63 and 177 inclusions were measured per specimen face, and principal strain ratios calculated on that basis. Using sets of 100 measurements, ten separate strain ratios were calculated for each sample size of 10, 15, 20, … 45 inclusions drawn at random from each data set. Only about 35 inclusions need to be measured per specimen face to obtain strain ratios within ± 10%.