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Populations and Sampling

Populations and Sampling. Population = group of people you need to know information about Census = information obtained from every person in population Sample = small group from within the population Sample survey = investigation done using a sample. Type of sample is important.

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Populations and Sampling

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  1. Populations and Sampling

  2. Population = group of people you need to know information about • Census = information obtained from every person in population • Sample = small group from within the population • Sample survey = investigation done using a sample

  3. Type of sample is important • Too small = results might not be reliable • Too big = too time consuming and expensive (but more accurate) • Can’t be biassed to one type of person over another.

  4. Sampling Methods • Simple Random Sample = each person in the population has an equal chance of being selected (eg names in a hat, random no. generator on calc) • Stratified Sampling = when population can be split into separate groups or strata and an equal proportion of each strata is selected • Systematic Sampling = choose items at regular intervals from an unordered list (eg every 10th one )

  5. Quota Sampling = population divided into groups (eg age groups) and a quota of people from each group is surveyed (interviewer decides who to interview from each group. • Cluster Sampling = population split into groups (clusters) some clusters are chosen and every item in the cluster is looked at. • Convenience Sampling = taking the easiest people to survey (eg first 100 people you meet)

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