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Chapter 1 Notes by Steven Grindle
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The method used to collect sample data is crucial because
1. no amount of statistical analysis will save poorly collected data.
2. the correct method of statistical analysis depends on the data collection method.
While we will not do much data collection in this class you need to be aware of the methods of sampling available
For the statistical techniques taught in this class to work, we must choose a sample that will be representative of the population as a whole. Thus we always will assume that simple random sampling has been done unless specified otherwise.
In chapter
7 we learn use a representative samples to make estimates of important population parameters.
Types of samples include
A random sample insures that every individual member of the population has an equal chance of being included.
A simple random sample insures that every individual member and every possible sample of the same size has an equal chance of being included.
A stratified sample requires that the population be partitioned into subgroups, such as male and female, prior to sampling.
A systematic sample involves selecting every nth entity from a population.
Any sample that is easy to get is a convenience sample.
Cluster sampling breaks the population into small clusters. Every item from a few randomly chosen clusters are analyzed