The mean sum-of-fractions for building surfaces is optional for computing the power of rejecting the null hypothesis and is calculated as follows:
\begin{equation} Mean_{\text{sof}} = \frac{Mean_{alpha}}{DCGL_{alpha}}+\frac{Mean_{beta}}{DCGL_{beta}}+\frac{Mean_{gamma}}{DCGL_{gamma}} \end{equation}
Where \(Mean_{alpha}\) is the total mean for the alpha activity and \(DCGL_{alpha}\) is the gross DCGL for the alpha activity, etc.
You can also choose to enter the estimated mean manually by setting the Manual / Auto Selector.