the complementary binomial distribution is defined by $$\Phi(a;n,p)=\sum _{j=a}^n \binom{n}{j} p^j(1-p)^{n-j},\;\;0<p<1,\;\;0\leq a\leq n.$$ see <A HREF="http://www.worldresearchlibrary.org/up_proc/pdf/1124-15114160424-7.pdf">The derivation of diffusion-jump modes for power plant projects under risk</A>