Historically one combines the partial half-life for a particular decay with the calculated phase-space factor \( f \) to obtain an ft value given by $$ f t_{1/2}=\frac{C }{\left[B(F_{\pm})+(g_{A}/g_{V})^{2} B(GT_{\pm}) \right] } $$ where $$ C = \frac{{\rm ln}(2)K_{o}}{(g_{V})^{2}}. $$