In the following slides were going to work with the concept of contrasts. The contrast is also called the total effect and it is a very simple way to calculate the effect and the sum of squares of any factor or interaction.

Let’s start with the contrast of the substrate, our Factor A. The contrast of the substrate is given by the sum of all treatments where the substrate is tested at its high level, minus the sum of all treatments where the substrate is tested at its low level. is tested at its high level, minus the sum of all treatments where the substrate is tested at its low level: The contrast of A given by ab plus a minus b minus one. In our case, 50.

In the same way we have the contrast of factor B, the enzyme. The contrast of the enzyme is given by the sum of all treatments where the enzyme is tested at its high level, minus the sum of all treatments where the enzyme is tested at its low level. The contrast of the enzyme B is given by ab plus b, minus a, minus one: minus 30 in our case.

And finally, we have the contrast of the interaction AB. The contrast of the interaction is given by the sum of the treatments where A B, substrate and enzyme, are both tested at their high levels or low levels, minus the treatment where one of them is at its high level while the orther is at its low level, then contrast of AB is given by ab plus one minus a minus b. in our case: 10.