subgroups, populations, genotypes, species, subspecies, phenotype, subsets, taxa, subtype, histologies, bacteroides, immunoreactivity, haplotype, alleles, loci, mus musculus, subfamilies, subregions, ecotypes, serum albumin, mutations, lactobacilli, lineages, epitope, penetrance, syngeneic, vivax, leydig cell, cellularity, metazoan, peromyscus, heterozygote, thiazide, lymphomas, heterozygosity, hepatoma, epistasis, phylogenies, tocopherol, homozygosity, mosaicism, pcr, viraemia, metaplasia, epithelia, etiologies, karyotype, bacteriuria, superinfection, thyrotropin, trimer, glycolipids, glycoproteins, csa, immunopathology, autoantibodies, polymorphism, myeloid, hypercholesterolemia, herpesviruses, leucocytes, erythropoiesis, granulocyte, ciliates, lymphocytic, glucuronide, carcinoid, estrone, anaerobes, codons, blastomeres, acropora, orcinus orca, mycobacteria, proteoglycan, parasitaemia, serologic, antigens, lymphocytosis, subclasses, clostridia, introgression, viremia, trichinella, proband, atopic, phyla, univariate, chlorthalidone, homologues, tetramer, faunas, lipid, nucleoside, anterior pituitary, tropomyosin, erythrocytes, metabolites, clade, bile acid, amphipods, pongo pygmaeus, subpopulation, subsamples, clones, groups, subcategories, collectivities, subareas, subgroup, effectors, group, organelles, subsections, subtypes, subunits, departments

proportional sampling, representative sampling, stratified sampling