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 not affected by other variables in the experiment. They are manipulated or varied in an experimental study to explore their effects. Some common independent variables include time, space, density, mass, fluid flow rate, and previous values of some observed value of interest. In statistical modeling and experimental sciences, dependent and independent variables are studied under the supposition or demand that they depend, by some law or rule, on the values of other variables.