SamplingJacqueline Corcoran, Ph.D.Research in Clinical Social Work Practice Virginia Commonwealth UniversitySchool of Social Workhttp://www.jacquelinecorcoran.com/

Sampling How will we get our participants? The sample is the who of the research

Ideally want to be representative

Representative sample – looks like actual population

Unrepresentative - a sample in which some characteristics are over-represented or under-represented relative to the total population

Population sample- a study of the entire population

How to sample: identifyTheoretical (universal) populationgroup to whom the study's

results are expected to apply PopulationSampling frame– the aggregation of elements from which the sample is selected.

How is a sampling frame different from population?

Time frameOpen vs. closed cases

Sampling Methods based onthe representativeness of the

populationconvenience and time constraintsaccess to the population

Probability samples Involve random selection each element has an equal chance of

selection that is independent of any other event in the selection process.

Types of probability sampling methods Simple random sampling Systematic random sampling Stratified random sampling

Simple random

everyone in the population has an equal chance of being included in the sample

Stratified random sampling to ensure that we have appropriate

proportions of what we need divide population into strata that are

important take the same percentage from each group

(i.e., 10%) – proportionate stratified sampling

can also take a larger proportion of very small homogenous groupings than the larger ones – disproportionate stratified sampling