diff --git a/R/titvFPEst.R b/R/titvFPEst.R
index fbf13ccd7..d963565bc 100755
--- a/R/titvFPEst.R
+++ b/R/titvFPEst.R
@@ -122,4 +122,18 @@ plotQsamples <- function(depths, Qs, Qmax) {
     }
 
     legend("topleft", paste("Q", Qs), fill=cols)
-}
\ No newline at end of file
+}
+
+pCallHetGivenDepth <- function(depth, nallelesToCall) {
+  depths = 0:(2*depth)   
+  pNoAllelesToCall = apply(as.matrix(depths),1,function(d) sum(dbinom(0:nallelesToCall,d,0.5)))
+  dpois(depths,depth)*(1-pNoAllelesToCall)
+}
+
+pCallHets <- function(depth, nallelesToCall) {
+  sum(pCallHetGivenDepth(depth,nallelesToCall))
+}
+
+pCallHetMultiSample <- function(depth, nallelesToCall, nsamples) {
+  1-(1-pCallHets(depth,nallelesToCall))^nsamples
+}