What is an Independent Variable?
An independent variable has a variety of meanings, depending on the discipline using the term. In science, for example, it is the variable that is being manipulated so that the change in another variable, referred to as the dependent variable, can be measured. In math, an independent variable is the variable that indicates the value of the independent variable. One of the biggest challenges many people have to deal with when looking at an independent variable is the fact that all variables depend on something. While that may be true, there is an easy way to determine what this variable is. Simply ask the question: What do I need to change in order to influence, or try to influence, another thing? The thing that needs changed would be your independent variable. Another way to look at it is to understand that this variable is the one you can control. This is true for independent variables in both science and statistics. A dependent variable cannot be controlled, but can be influenced. Fo
A variable that you believe might influence your outcome measure. This might be a variable that you control, like a treatment, or a variable not under your control, like an exposure. It also might represent a demographic factor like age or gender. Contrast this with the definition of the dependent variable. An independent variable is a hypothesized cause or influence on a dependent variable. One way to distinguish these variables is to ask yourself what you are want to learn from this research. The dependent variable is a variable you are trying to predict. Any variable that you are using to make those predictions is an independent variable. A recently published research study examined the relationship of dietary fat consumption and the development of ischemic stroke in a cohort of 832 men who were free of cardiovascular disease at baseline (1966-1969) and who were followed for a twenty year period. In this study, the independent variables were: • percentage of total fat in the diet, •
