Experimental studies manipulate factors to determine their effects.
An experimental study involves manipulating one variable (called an independent variable) to determine its effect on another variable (a dependent variable). An example of a manipulated variable (independent variable) can be hours of sleep, and the dependent variable (resulting variable) can be speed of reflexes. Hours of sleep (independent variable) can be manipulated (increased or decreased) to see the result it has on speed of reflexes (outcome or dependent variable).