Index: mod/quiz/report/statistics/statistics_table.php
===================================================================
--- mod/quiz/report/statistics/Copy of statistics_table.php	Tue Oct 07 15:30:01 2008
+++ mod/quiz/report/statistics/statistics_table.php	Tue Oct 07 15:30:42 2008
@@ -167,7 +167,7 @@
     }
     
     function col_sd($question){
-        if (!is_null($question->_stats->sd)){
+        if (!is_null($question->_stats->sd) && $question->_stats->maxgrade){
             return number_format($question->_stats->sd*100 / $question->_stats->maxgrade, 2).'%';
         } else {
             return '';
@@ -181,7 +181,11 @@
         }
     }
     function col_facility($question){
-        return number_format($question->_stats->facility*100, 2).'%';
+        if (!is_null($question->_stats->facility)){
+            return number_format($question->_stats->facility*100, 2).'%';
+        } else {
+            return '';
+        }
     }
 // ou-specific ends - whole file is local until Moodle 2.0
 }
Index: mod/quiz/report/statistics/qstats.php
===================================================================
--- mod/quiz/report/statistics/Copy of qstats.php	Tue Oct 07 15:31:43 2008
+++ mod/quiz/report/statistics/qstats.php	Tue Oct 07 15:32:05 2008
@@ -137,7 +137,11 @@
 
     function _initial_question_walker(&$stats){
         $stats->gradeaverage = $stats->totalgrades / $stats->s;
-        $stats->facility = $stats->gradeaverage / $stats->maxgrade;
+        if ($stats->maxgrade){
+            $stats->facility = $stats->gradeaverage / $stats->maxgrade;
+        } else {
+            $stats->facility = null;
+        }
         $stats->othergradeaverage = $stats->totalothergrades / $stats->s;
         sort($stats->gradearray, SORT_NUMERIC);
         sort($stats->othergradesarray, SORT_NUMERIC);