diff --git a/trunk/paradiseo-mo/src/sampling/moStatistics.h b/trunk/paradiseo-mo/src/sampling/moStatistics.h
index 960a39ffb..7c74cbc16 100644
--- a/trunk/paradiseo-mo/src/sampling/moStatistics.h
+++ b/trunk/paradiseo-mo/src/sampling/moStatistics.h
@@ -91,7 +91,7 @@ public:
 
             avg /= n;
 
-            std = std / n - avg * avg ;
+            std = (std / n) - avg * avg ;
             if (std > 0)
                 std = sqrt(std);
         }