diff --git a/CLPBN/learning/example/school_params.yap b/CLPBN/learning/example/school_params.yap
index abe26f891..7f18f38de 100644
--- a/CLPBN/learning/example/school_params.yap
+++ b/CLPBN/learning/example/school_params.yap
@@ -11,22 +11,31 @@ main :-
         em(L,0.1,10,CPTs,Lik),
         writeln(Lik:CPTs).
 
+missing(0.1).
+
 % miss 30% of the examples.
 goal(professor_ability(P,V)) :-
         pos:professor_ability(P,V1),
-        ( random > 0.3 -> V = V1 ; true).
+	missing(X),
+        ( random > X -> V = V1 ; true).
 % miss 10% of the examples.
 goal(professor_popularity(P,V)) :-
         pos:professor_popularity(P,V1),
-        ( random > 0.3 -> V = V1 ; true).
+	missing(X),
+        ( random > X -> V = V1 ; true).
 goal(registration_grade(P,V)) :-
         pos:registration_grade(P,V1),
-        ( random > 0.1 -> V = V1 ; true).
+	missing(X),
+        ( random > X -> V = V1 ; true).
 goal(student_intelligence(P,V)) :-
         pos:student_intelligence(P,V1),
-        ( random > 0.1 -> V = V1 ; true).
+	missing(X),
+        ( random > X -> V = V1 ; true).
 goal(course_difficulty(P,V)) :-
         pos:course_difficulty(P,V1),
-        ( random > 0.1 -> V = V1 ; true).
+	missing(X),
+        ( random > X -> V = V1 ; true).
 goal(registration_satisfaction(P,V)) :-
-        pos:registration_satisfaction(P,V).
+        pos:registration_satisfaction(P,V1),
+	missing(X),
+        ( random > X -> V = V1 ; true).