What are the dependent, independent & extraneous variables? Explain with suitable examples.Posted question is related with - Research Methodology

In research, a variable is defined as any factor that can be manipulated and measured. In a research variables take on different values which are observed and measured to draw conclusion about the subject under study.

Variables are grouped in many different types and according to their nature. One of the ways of classifying the variable is depending upon the way these take on different values during a research or experiment and the nature of influence they have on the research outcomes. As per this classification variables are classified as dependent, independent and extraneous variables.

Independent variables are isolated and controlled by the researcher during the experiment or the research study. The dependent variable changes as a result of, or in response to, the variations in the dependent variable. Extraneous variable are neither manipulated by the researcher nor change in response to changes in independent variables, but which may have some influence on the outcome of an experiment including the values of the dependent variables. Therefore researchers try to ensure that there is no changes in the values taken by the extraneous variable during an experiment.

To understand these term better let us take the example of impact of a particular nutrient, say calcium, on increase in weight of rats. A researcher can study this by feeding different quantities of calcium to different rats and observing the increase in their weight. In this case the quantity of calcium in the diet of a rat is the independent variable, and the increase in weight of the mouse is dependent variable. However, increase in weight of rats also depends on other variables such as other nutrients in their diet, their original weight, and living conditions of mice. These are the extraneous variable. The researcher can eliminate the impact of these extraneous variable by ensuring that all the rats used in the experiment have comparable age and weight at the start of experiment and live under similar condition during the experiment. Also he or she will ensure that diet fed to all the rats is identical except for the quantity of calcium.