A dependent variable is a variable that changes as a result of the manipulation of the independent variable in an experiment. It is the outcome that researchers are interested in measuring, and it "depends" on the independent variable. Dependent variables are also called response variables, outcome variables, or left-hand-side variables. In contrast, independent variables are variables that are manipulated or varied in an experimental study to explore their effects. They are not seen as depending on any other variable in the scope of the experiment in question. Some common independent variables include time, space, density, mass, fluid flow rate, and previous values of some observed value of interest. In an experiment, any variable that can be attributed a value without attributing a value to any other variable is called an independent variable.