Sampling

 

Who? How many? Selection? Sorted?

 

Information:

          Gender

          Age

          Geographical area

          SES

          Source

          Basis for participation

          Other

 

Population:

          All the units we would like to study

          The people who are the focus of the research

 

Sample:

          A group of people who represent the population

 

Keep record of:

          Number contacted

          Number participated

          Number screened out and why

          Number dropped out and why

 

Probability sampling:

          Simple random

          Systematic sampling

          Stratified random

          Cluster

 

Nonprobability sampling:

          Convenience

          Purposive

          Snowball

          Quota

 

 

 

Sampling error:

          Random

          Systematic

 

Probability theory:

          To estimate how closely sample statistics are clustered around the true population value.

          Large samples

          Numerous samples

          Randomness (sample with replacement)

 

Randomness is necessary in order to use powerful statistics!