The core consists of making meaningful statements about the population of individuals based on the information contained in the measured group of individuals. The data consist of measured or observed values on certain common characteristics or attributes of the individuals. The goal of data analysis is to make statements about properties of variables, individually or collectively. Variables are classified according to their use in statistics. The major division classifies variables according to whether they are numerical or categorical.
Categorical variables take on values from a finite set of possible levels.
A level is a label for a non-numeric value. If the possible levels are ordered, the categorical variable is said to be ordered or ranked . Exercise 1 gives a series of statistical situations in which the objective is to identify the individual, specify the variable type, and give possible values of the variable.