In an experiment, it is important that independent and dependent variables are given which specify procedures for manipulating the independent variable and measuring the dependent variable.

a relationship ( model equation)

Step-by-step explanation:

the relationship specifies how the dependent variable relies on the independent variable.This helps in manipulating of the variable to see its effect/outcome.The relationship can be mathematical or logical ; it can also be a set of algorithm (program) which can be worked on using the independent variables as inputs. Usually the independent variables influence the dependent variables.