Awon irojinle alawujo tabi irojinle awujo je awon ilana isese onirojinle ti wo unje lilo lati se agbeka ati se itumo awon isele awujo larin inu ile-eko ironu pati kan.. 
While it is usually best to Sample Randomly, concern with differences between spearagu subpopulations sometimes calls for straTífí samplingling.. 