--- a/src/tools/model/average.h	Fri Aug 31 12:24:28 2012 +0200
+++ b/src/tools/model/average.h	Sat Sep 01 20:57:21 2012 +0200
@@ -85,7 +85,7 @@
   /// Unbiased estimate of variance
   double   Var     () const { return m_varianceCalculator.getVariance ();}
   /// Standard deviation
-  double   Stddev  () const { return sqrt (Var ()); }
+  double   Stddev  () const { return std::sqrt (Var ()); }
   //\}
 
   /** 
@@ -98,11 +98,11 @@
    */
   //\{
   /// Margin of error of the mean for 90% confidence level 
-  double   Error90 () const { return 1.645 * sqrt (Var () / Count ()); }
+  double   Error90 () const { return 1.645 * std::sqrt (Var () / Count ()); }
   /// Margin of error of the mean for 95% confidence level 
-  double   Error95 () const { return 1.960 * sqrt (Var () / Count ()); }
+  double   Error95 () const { return 1.960 * std::sqrt (Var () / Count ()); }
   /// Margin of error of the mean for 99% confidence level 
-  double   Error99 () const { return 2.576 * sqrt (Var () / Count ()); }
+  double   Error99 () const { return 2.576 * std::sqrt (Var () / Count ()); }
   //\}
 
 private: