Revision:Sampling Methods

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Random - Every member of the population has an equal chance of being selected.

Systematic - Every member of the sample is chosen at regular intervals from a list

Stratified - Population split in to groups (strata). Each group needs to be fairly represented in sample. Number in each group is proportional to the group size in the population.

Quota - Used in Market Research. Interviewer questions certain people of certain types (over 60, Under 21, Car Owner etc). Interviewer makes the choise of person and can lead to a bias.

Cluster - Population is divided into small groups called clusters. Clusters are chosen randomly, and then the sample would be every person in the cluster. On allocation of people to their respectively cluster, there could be the introduction of a bias.