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We have many ways to describe a collection of data. We will explain and illustrate many such ways in this section.
There is a distinction that should be made at this point. We distinguish between population and sample characteristics by referring to population characteristics as population parameters and sample characteristics as sample statistics. Thus, the mean of a population is a parameters of that population, but the mean of a sample is a statistic of that sample. Beyond that distinction there is no difference in the naming or computing for the measures mode, the median, the range, and the quartiles. The mean of a population, μ, has a different symbol from the one used for the mean of a sample, , however the computation of each is the same. Standard deviation has both different symbols, σ for a population and s_{x} for a sample, and slightly a slightly different formula. That difference will be illustrated in the subsequent web page measures of dispersion.