A statistical two-sided z-test is applied to determine whether a measured micrograph is likely to have come from a randomly dispersed material, of the form:(4)Z=(ADDel(test)-E(ADDel(HR)))/SAD(HR),where ADDel(test) is the measurement from the material, E (ADDel(HR)) and SAD(HR) are the mean and standard deviation, respectively, of the null-hypothesis HR model.