$$y=F（X|{\nu }_1那{\nu }_2）=\frac{\mathrm{\gamma .}\left[\frac{（{\nu }_1+{\nu }_2）}{2}\right]}{\mathrm{\gamma .}（\frac{{\nu }_1}{2}）\mathrm{\gamma .}（\frac{{\nu }_2}{2}）}{（\frac{{\nu }_1}{{\nu }_2}）}^{\frac{{\nu }_1}{2}}\frac{X^{\frac{{\nu }_1-2}{2}}}{{\left[1+（\frac{{\nu }_1}{{\nu }_2}）X\right]}^{\frac{{\nu }_1+{\nu }_2}{2}}}$$

$$F（{\nu }_1那{\nu }_2）=\frac{\raisebox{1ex}{${\chi }_1$}\!\left/ \!\raisebox{-1ex}{${\nu }_1$}\right.}{\raisebox{1ex}{${\chi }_2$}\!\left/ \!\raisebox{-1ex}{${\nu }_2$}\right.}$$