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 ID: 224799
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Slide1
Populations and SamplingSlide2
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 sampleSlide3
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.Slide4
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 10
th
one )Slide5
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)