COMM 291 Lecture 11: COMM 291 201 - Lecture 11 - Sampling and surveys
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Where do data come from ? voluntary surveys leg. Internet usually worthless experimental studies actively manipulate variables observational studies secondary sources sit back and watch eg . Examine part of the whole a how representative of the whole thing ? to sample population. If sample not representative then it"s biased . representative is getting. All characteristics of population in the sample . la. 2 samples you get will be different differences between samples is sampling variability or sampling error f mistake matters not population size o o o o. Sample ( srs ) each case has equal chances of being chosen. Stratified random sample split population into groups with similar characteristics then. Cluster random sample split population into groups with different characteristics each. Select cluster represents the population a few clusters at random.
