# How to calculate the main effects?

The calculation of the main effects from a factorial design of experiment is described with examples in Video 2 (both Video 1 and Video 2 are the same).

The average effect of the factor A (called the main effect of A) can be calculated from the average responses at the high level of A minus the average responses at the low level of A (Figure 2). When the main effect of A is calculated, all other factors are ignored assuming that we don’t have anything else other than the interested factor, which is A, the temperature factor.

Therefore, the main effect of the temperature factor can be calculated as A = (9+5)/2 - (2+0)/2 = 7-1 = 6. The calculation can be seen in figure 2.

= the average comfort increases by 6 on a scale of 0 (least comfortable) to 10 (most comfortable) if the temperature increases from 0- to 75-degree Fahrenheit.

Similarly, the main effect of B is calculated by ignoring all other factors assuming we don’t have anything else other than the interested factor, which is B, the humidity factor.

Therefore, the main effect of the humidity factor can be calculated as B= (2+9)/2- (5+0)/2=5.5-2.5=3. The calculation can be seen in figure 3.

= the average comfort increases by 3 on a scale of 0 (least comfortable) to 10 (most comfortable) if the relative humidity increases from 0 to 35 percent. Figure 2. Graphical representation of the main effect of the temperature (factor A). Figure 3. Graphical representation of the main effect of the humidity (factor B).