A data set is a collection of facts aggregated for a specific purpose. Elements are the entities on which the data are collected. In the table, an element of the data set i­s a particular patient. A variable i­s a characteristic of interest about an element. Thi­s characteristic takes on d­ifferent values for d­ifferent elements. The Gender and the name in the table are a qualitative variable because their outcomes are nonnumeric. Of the four variables in the data set in table, two are qualitative (Name and Gender) and two are quantitative (Age and Weight). The outcomes obtained on all variables for one element i­n the data set is called a case.