What is an independent varible, and dependent varible?

Answer 1

In experimentation, the independent variable is some characteristic of an experimental setup that can be changed at will. The experiment assumes that the independent variable is the cause of some phenomenon to be observed. The quantifications of that phenomenon are dependent variables. For example, you might alter the amount of light that different (but otherwise identical) plants receive. The available light is the independent variable. The dependent variables, which have to be measured, might include the plant's height or color over time.

In math, the indepedent variable is a variable that can be assigned any value (from a given domain) at will. The dependent variable's value is determined by the independent variable. By convention, x is the independent variable. For example, if we say that y = 2x + 3, then x is the independent variable. If we assign it a value of 6, then y, the dependent variable, has a value of 15.

Answer 2

I will only add a cautionary note to DavidK93’s answer. In empirical research, it is not always easy, or even always possible, to know which is the independent and which is the dependent variable. This is true even if you can build a perfectly good equation clearly showing that the 2 variables are related.

In DavidK93’s example, he can predict my y with his x. But then, I can predict his x with my y because x = (y-3) / 2. Sometimes you just don’t know – and that’s the way it is.