Читать книгу Applied Biostatistics for the Health Sciences - Richard J. Rossi - Страница 52

For a well-defined population of units and a variable, say X, the collection of all possible values of the variable X formed by measuring all of the units in the target population forms the population associated with the variable X. When multiple variables are recorded, each of the variables will generate its own population. Furthermore, since a variable may take on many different values, an important question concerning the population of values of the variable is “How can the population of values of a variable be described or summarized?” The two different approaches that can be used to describe the population of values of the variable are (1) to describe explicitly how the variable is distributed over its values and (2) to describe a set of characteristics that summarize the distribution of the values in the population.