Considering the three cases are found in (b) and (c) the change of the response under level 1 and 2 of the A to change the conditions of factor B from level 1 to level 2. There is not the same, so case (b) and (c) the level that demonstrate the interaction between factor A and factor B, but for the case of (a) the change of the response under level 1 and. A factor of two when changing the conditions of factor B from the first level to the second level, a constant (equal) is equal to 2, so in this case, the trial did not appear to affect joint.