Business and Economic Statistics Stratified and Clustered Sampling

Business and Economic Statistics: Stratified and Clustered Sampling Presenter: Sam Capurso

Objectives • Be able to explain and apply the • following concepts: - Stratified Sampling - Clustered Sampling • Give examples of strata and clusters • Explain why you would use Stratified Sampling and Clustered Sampling

Use this as. . . • A refresher • Or • To resolve any knowledge gaps you have

Stratified Sampling • Split the population into groups (strata) whereby: - Each stratum is the same within - Each stratum is different between • Take a SRS from each stratum • Be careful! You can’t have more than one of the same strata Strata Different characteristics

Clustered Sampling • Select or construct groups (clusters) whereby: - Each cluster is roughly the same as the others - The clusters are representative of the entire population Clusters • Randomly select clusters and then take a census of these • Be careful! CS is not SRS! Random Selection

Application • What are some examples of strata? • What are some examples of clusters? • Scenario: You want to survey nurses in Australian hospitals to ask their attitudes towards their work conditions and pay

Why conducted Stratified Sampling? • You have reason to believe that people of a similar characteristic will respond in a particular way • You want to reduce variability in the samples ? • You want to reflect proportions of groups in the population

Why conducted Clustered Sampling? • Reduce costs • Convenience (not convenience sampling!) • Practicality $

Summary Stratified Sampling (SS) Clustered Sampling (CS) Groups same within: homogenous Groups have no defining characteristic – are representative of population: heterogeneous Groups are different from each other Groups are roughly the same as each other SRS taken from each group Census taken from each group Know examples of strata Know examples of clusters Know reasons for conducting Stratified Sampling Know reasons for conducting Clustered Sampling End

Please note _(this was shown before the presentation) • As you know, I am currently undertaking a Certificate IV in Training and Assessment at TAFE SA • This presentation is being recorded, and will be submitted for assessment

Terminology P n o i t la u p o _slide 4 (for assessor only) m o d an ) R le (SRS p Sim ple Sam d e i f i at ng r t S li p Sam Stra & m tu a t a r st d e r e st u l g C n i l p m a S s u s en C New terms in bold