1. adj. Able to vary in quantity or magnitude.

2. n. The properties of an object which can take on different values. A continuous variable can be found at any point on a continuous scale (e.g. height). A dependent variable (response variable) is a factor whose values in different treatment conditions are compared: that is, the researcher is interested in determining if the value of the dependent variable varies when the values of another variable (the independent variable) are varied, and by how much; the independent variable is said to cause an apparent change in, or simply affect, the dependent variable. A dichotomous variable has two categories (e.g. gender: male and female). A discrete variable can be found only at fixed points and is expressed in whole units or mutually exclusive categories (e.g. numbers of teeth). Interval data is measured on a scale of which the intervals are equal. Nominal variables classify data into categories (e.g. male, female). Ordinal variables rank data according to degree; they indicate only that one data point is ranked higher or lower than another. A predictor variable tries to predict values of another variable (the outcome variable). A quantitative variable takes a numerical value e.g. DMF score; a qualitative variable takes a non-numerical value or defines a characteristic e.g. sex (M or F).