Lecture 04
A Variable
A variable is a characteristic of an individual which take different values at different situations, e.g. age, height, weight, smoking habit etc.
Types of Variables
Variables / data of a planned experimental study may be classified into 2 main categories:
Qualitative / Categorical
Population is classified into various categories and data is recorded in the form of “counts”, this is called qualitative data / variables. For example gender (male, female), eye color, hair color, complexion of skin etc.
These variables are measured as discrete / discontinuous numbers (no decimal places, and cannot be divided into fractions). For example number of rats in an experiment.
Quantitative / Numerical
When we make observations numerically and the variable to be measured is numerical value then this is called qualitative data / variable. For example blood glucose level, height etc.
These variables are measured as continuous numbers that is capable of taking every possible value between two given numbers is termed as continuous. For example, age, weight (52.5 kg).
Variables are also classified based upon their relationship with each other
Dependent and Independent Variables
A dependent variable is also called a response variable, i.e. its value depends upon value of some other variable.
An independent variable is sometimes called a predictor variable, it is usually set or changed by the experimenter.
For example, prevalence of a disease in different age groups; in this study age is independent variable and prevalence of disease is dependent variable.
