RANDOM STRATIFIED SAMPLE Stage 1: Identify those characteristics which appear in the wider population which must also appear in the sample, i.e. divide the wider population into mutually exclusive homogeneous groups. Stage 2: Randomly sample within these groups, the size of each group being determined by judgement or tables of sample size.

THE PROBLEM OF STRATA N S Total Whole company 1,000 278 278 English employees 800 260 Scottish employees 100 80 Welsh employees 50 44 American employees 50 44 428

SCHOOLING SUB-TOTAL SAMPLE SIZE No schooling 35,020 380 Pre-primary 6,811 364 Primary incomplete 80,285 384 Primary complete 109,561 Junior secondary 94,491 Senior secondary 66,250 382 Tertiary, non-degree 7,481 367 Tertiary, degree 23,944 379 Special 360 186 Total 424,203 3,210 BUT . . . Total without strata 384

PROBLEMS OF STRATA The greater the number of strata, the larger the sample will be. Therefore, keep to as few strata as necessary.