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