1. STRATIFIED SAMPLING DEFINITION Strata: groups of members that share common characteristics Stratified sampling: the population is divided into subpopulations (strata) and random samples are taken of each stratum Stratified sample: has the same proportion of members from each stratum as the population does 1

2. EXAMPLE A population of 600 men and 500 females is going to be sampled. The proposed sample size is 300. If the company hired to sample this population will be using a stratified sampling technique, how many of each sex will be sampled? 2 ProsCons Unbiased estimates may reduce sampling variance Enables standard statistical methods Precision depends on sample size More control May not provide representative sample No exact estimate for variances No variety

3. EQUATION 3

4. PROCESS 4 Population: male, full time: 90 male, part time: 18 female, full time: 9 female, part time: 63 Total: 180 Sample size: male, full time: 20 male, part time: 4 female, full time: 2 female, part time: 14 Total: 40

5. USING THE EQUATION 5