 Any factor that can exist in varying amounts or types  Parts of an experiment that impact an outcome

 Control  Independent (Manipulated)  Dependent (Responding)  Constant

 Variable that is constant and unchanged  Strongly influences values (other variables)  We compare everything else to the control

 Manipulated Variable  The variable you vary to see how it may affect the dependent variable

 Responding Variable  The variable you measure as a result of changing the independent variable

 It is important to KEEP ALL VARIABLES CONSTANT, EXCEPT FOR THE INDEPENDENT VARIABLE  Provides best results