tk/Multinomial_test: fixed data non-zero count

lib/tk/multinomial_test.ml

@@ -14,7 +14,7 @@ let data ~x1 ~x2 =
 
 let data_nz d =
   Array.counti d.x1 ~f:(fun i _ ->
-      d.x1.(i) <> 0 && d.x2.(i) <> 0
+      d.x1.(i) <> 0 || d.x2.(i) <> 0
     )
 
 type result = {