what are constant and manipulated variables
1 Responding (or Dependent) Variable: This is the variable that changes as a result of the changes in the manipulated variable. 2  In our fertilizer example, the responding variable would be the size of the plants. 3  Controlled Variables (or Controls): These are all the things that you will keep the same in your experiment. Responding (or Dependent) Variable: This is the variable that changes as a result of the changes in the manipulated variable. 2  In our fertilizer example, the responding variable would be the size of the plants. 3  Controlled Variables (or Controls): These are all the things that you will keep the same in your experiment.