Statistical Measures

Frequency Distributions

• Variables

• The values of a variable may be
• numbers (for example, number of tacos eaten);
• an ordered numerical scale (for example, age); or,
• categories (for example, ill or well), called a “nominal scale” because the categories are named.
• In epidemiology we often deal with variables that have only two categories, like alive or dead, ill or well, did or did not eat the potato salad.
• Any of these types of data may be summarized in a frequency distribution (See Table 3, which shows a variable with only two possible values).