MDL-14204 "Content for Quiz Statistics report table - Random_guess_score" added method random_guess_score to question type objects and a new function in questionlib that calls the question type method.

question/type/match/questiontype.php

@@ -425,6 +425,16 @@ class question_match_qtype extends default_questiontype {
         // This should almost certainly be overridden
         return substr(implode(', ', $this->get_actual_response($question, $state)), 0, $length);
     }
+    
+        
+    /**
+     * @param object $question
+     * @return integer a score out of 1 that the average random guess by a
+     * student might give.
+     */
+    function get_random_guess_score($question) {
+        return 1 / count($question->options->subquestions);
+    }
 
 /// BACKUP FUNCTIONS ////////////////////////////
 

question/type/multianswer/questiontype.php

@@ -514,6 +514,19 @@ class embedded_cloze_qtype extends default_questiontype {
         }
         return $responses;
     }
+    
+    /**
+     * @param object $question
+     * @return integer a score out of 1 that the average random guess by a
+     * student might give.
+     */
+    function get_random_guess_score($question) {
+        $totalfraction = 0;
+        foreach (array_keys($question->options->questions) as $key){
+            $totalfraction += get_random_guess_score($question->options->questions[$key]);
+        }
+        return $totalfraction / count($question->options->questions);
+    }
 
 /// BACKUP FUNCTIONS ////////////////////////////
 

question/type/multichoice/questiontype.php

@@ -396,7 +396,18 @@ class question_multichoice_qtype extends default_questiontype {
     function response_summary($question, $state, $length = 80) {
         return implode(',', $this->get_actual_response($question, $state));
     }
-
+    /**
+     * @param object $question
+     * @return integer a score out of 1 that the average random guess by a
+     * student might give.
+     */
+    function get_random_guess_score($question) {
+        $totalfraction = 0;
+        foreach ($question->options->answers as $answer){
+            $totalfraction += $answer->fraction;
+        }
+        return $totalfraction / count($question->options->answers);
+    }
 /// BACKUP FUNCTIONS ////////////////////////////
 
     /*

question/type/questiontype.php

@@ -674,7 +674,15 @@ class default_questiontype {
             return null;
         }
     }
-
+    
+    /**
+     * @param object $question
+     * @return integer a score out of 1 that the average random guess by a
+     * student might give.
+     */
+    function get_random_guess_score($question) {
+        return 0;
+    }
     /**
     * Return the actual response to the question in a given state
     * for the question

question/type/random/questiontype.php

@@ -101,7 +101,7 @@ class random_qtype extends default_questiontype {
                          AND parent = '0'
                          AND hidden = '0'
                          AND id NOT IN ($cmoptions->questionsinuse)
-                         AND qtype NOT IN ($QTYPE_EXCLUDE_FROM_RANDOM)", '', 'id')) {
+                         AND qtype NOT IN ($QTYPE_EXCLUDE_FROM_RANDOM)", array(), '', 'id')) {
                 $this->catrandoms[$question->category][$question->questiontext] =
                         draw_rand_array($catrandoms, count($catrandoms));
             } else {

question/type/randomsamatch/questiontype.php

@@ -272,7 +272,20 @@ class question_randomsamatch_qtype extends question_match_qtype {
         $result->responses = $answers;
         return $result;
     }
-
+    /**
+     * @param object $question
+     * @return integer a score out of 1 that the average random guess by a
+     * student might give.
+     */
+    function get_random_guess_score($question) {
+        //Effectively $subquestions multi choice questions with equal weighting
+        //assuming a student has the intelligence to not select the same answer twice
+        //there is in each subquestion factorial($subquestions-1) chance of getting
+        //the answer right. There are factorial($subquestions) possible combinations of
+        //answers and it works out to an average grade of 1/$subquestions.
+        $subquestions = count($question->options->subquestions);
+        return 1/$subquestions;
+    }
 /// BACKUP FUNCTIONS ////////////////////////////
 
     /*

question/type/shortanswer/questiontype.php

@@ -239,7 +239,20 @@ class question_shortanswer_qtype extends default_questiontype {
         }
         return $response;
     }
-
+    /**
+     * @param object $question
+     * @return integer a score out of 1 that the average random guess by a
+     * student might give.
+     */
+    function get_random_guess_score($question) {
+        $answers = &$question->options->answers;
+        foreach($answers as $aid => $answer) {
+            if ('*' == trim($answer->answer)){
+                return $answer->fraction;
+            }
+        }
+        return 0;
+    }
     /// BACKUP FUNCTIONS ////////////////////////////
 
     /*

question/type/truefalse/questiontype.php

@@ -245,6 +245,14 @@ class question_truefalse_qtype extends default_questiontype {
         }
         return $responses;
     }
+    /**
+     * @param object $question
+     * @return integer a score out of 1 that the average random guess by a
+     * student might give.
+     */
+    function get_random_guess_score($question) {
+        return 0.5;
+    }
 
 /// BACKUP FUNCTIONS ////////////////////////////