The ratio of the sampling variance of the complex sample to that of a simple random sample of the same size is the design effect, or 'deff' (which is equal to the deft squared).
Y gymhareb rhwng amrywiant samplu y sampl cymhleth a sampl syml a ddewiswyd ar hap o'r un maint yw'r 'deff' (design effect, sy'n cyfateb i'r deft wedi ei sgwario).