Answer:
The variable is defined as the trait, factor, or condition that exist in different types or amounts.
In an experiment, there exist three types of variables:
Independent variable: It is the variable which is changed by the scientist. It includes the things or factors whose effects are being studied. For example, level of sugar in the diet is an independent variable.
Dependent variable: It is the variable value of which depends on the value of the independent variable. For example, the weight of the mice will be a dependent variable in this hypothesis.
Controlled variables: These are the variables whose values are kept constant during an experiment. For example, temperature or other living conditions of all the mice used in the experiment.