Review
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population: all subjects of interest
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sample: the subset of the population for whom we have data
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parameter: a numerical summary of the population
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statistic: a numerical summary of a sample take from the
population
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descriptive statistics: methods for summarizing the data
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inferential statistics: methods of making decisions or
predictions about a population
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Randomness!
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random sampling: each subject in the population has the
same chance of being included in the sample
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variable: any characteristic that is observed for the subject in
a study
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categorical variable: each observation belongs to one of a
set of categories
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quantitative: observations take numerical values that
represent different magnitudes of the variable
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discrete variable: a quantitative variable is discrete if its
possible values form a set of separate number, such as
0,1,2,. . .
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continuous variable: a quantitative variable is continuous if
its possible values form an interval
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frequency table