MDL-14208 'Improvement of Item Analysis Report : Cache results of calculations, "recompute now" functionality' - using new tables to cache stats results.

2008-07-24 13:25:07 +00:00
parent 23277af8f1
commit 71a2b878fa
6 changed files with 269 additions and 126 deletions
@@ -11,9 +11,9 @@ $string['quizinformation'] = 'Quiz information';
 $string['quizoverallstatistics'] = 'Quiz overall statistics';
 $string['quizname'] = 'Quiz name';
 $string['coursename'] = 'Course name';
-$string['nooffirstattempts'] = 'Number of first attempts';
-$string['noofallattempts'] = 'Total number of attempts';
-$string['statsfor'] = 'Statistics (for $a)';
+$string['firstattemptscount'] = 'Number of first attempts';
+$string['allattemptscount'] = 'Total number of attempts';
+$string['statsfor'] = 'Quiz Statistics (for $a)';
 $string['attempts'] = 'Attempts';
 $string['firstattempts'] = 'first attempts';
 $string['allattempts'] = 'all attempts';
@@ -25,13 +25,14 @@ $string['errormedian'] = 'Error fetching median';
 $string['errorpowers'] = 'Error fetching data to calculate variance for quiz grades';
 $string['errorpowerquestions'] = 'Error fetching data to calculate variance for question grades';
 $string['errorstatisticsquestions'] = 'Error fetching data to calculate statistics for question grades';
-$string['median'] = 'Median grade';
-$string['standarddeviation'] = 'Standard deviation';
-$string['skewness'] = 'Score distribution skewness';
-$string['kurtosis'] = 'Score distribution kurtosis';
-$string['cic'] = 'Coefficient of internal consistency';
-$string['errorratio'] = 'Error ratio';
-$string['standarderror'] = 'Standard error';
+$string['median'] = 'Median grade (for $a)';
+$string['standarddeviation'] = 'Standard deviation (for $a)';
+$string['standarddeviationq'] = 'Standard deviation';
+$string['skewness'] = 'Score distribution skewness (for $a)';
+$string['kurtosis'] = 'Score distribution kurtosis (for $a)';
+$string['cic'] = 'Coefficient of internal consistency (for $a)';
+$string['errorratio'] = 'Error ratio (for $a)';
+$string['standarderror'] = 'Standard error (for $a)';
 $string['questionnumber'] = 'Q#';
 $string['quizstructureanalysis'] = 'Quiz structure analysis';
 $string['questiontype'] = 'Q type';
@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<XMLDB PATH="mod/quiz/report/statistics/db" VERSION="20080724" COMMENT="XMLDB file for Moodle mod/quiz/report/statistics"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:noNamespaceSchemaLocation="../../../../../lib/xmldb/xmldb.xsd"
+>
+  <TABLES>
+    <TABLE NAME="quiz_statistics" COMMENT="table to cache results from analysis done in statistics report for quizzes." NEXT="quiz_question_statistics">
+      <FIELDS>
+        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="quizid"/>
+        <FIELD NAME="quizid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="groupid"/>
+        <FIELD NAME="groupid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="false" ENUM="false" PREVIOUS="quizid" NEXT="allattempts"/>
+        <FIELD NAME="allattempts" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="true" SEQUENCE="false" ENUM="false" COMMENT="bool used to indicate whether these stats are for all attempts or just for the first." PREVIOUS="groupid" NEXT="timemodified"/>
+        <FIELD NAME="timemodified" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="false" ENUM="false" PREVIOUS="allattempts" NEXT="firstattemptscount"/>
+        <FIELD NAME="firstattemptscount" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="false" ENUM="false" PREVIOUS="timemodified" NEXT="allattemptscount"/>
+        <FIELD NAME="allattemptscount" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="false" ENUM="false" PREVIOUS="firstattemptscount" NEXT="firstattemptsavg"/>
+        <FIELD NAME="firstattemptsavg" TYPE="number" LENGTH="15" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" DECIMALS="5" PREVIOUS="allattemptscount" NEXT="allattemptsavg"/>
+        <FIELD NAME="allattemptsavg" TYPE="number" LENGTH="15" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" DECIMALS="5" PREVIOUS="firstattemptsavg" NEXT="median"/>
+        <FIELD NAME="median" TYPE="number" LENGTH="15" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" DECIMALS="5" PREVIOUS="allattemptsavg" NEXT="standarddeviation"/>
+        <FIELD NAME="standarddeviation" TYPE="number" LENGTH="15" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" DECIMALS="5" PREVIOUS="median" NEXT="skewness"/>
+        <FIELD NAME="skewness" TYPE="number" LENGTH="15" NOTNULL="false" UNSIGNED="false" SEQUENCE="false" ENUM="false" DECIMALS="10" PREVIOUS="standarddeviation" NEXT="kurtosis"/>
+        <FIELD NAME="kurtosis" TYPE="number" LENGTH="15" NOTNULL="false" UNSIGNED="false" SEQUENCE="false" ENUM="false" DECIMALS="5" PREVIOUS="skewness" NEXT="cic"/>
+        <FIELD NAME="cic" TYPE="number" LENGTH="15" NOTNULL="false" UNSIGNED="false" SEQUENCE="false" ENUM="false" DECIMALS="10" PREVIOUS="kurtosis" NEXT="errorratio"/>
+        <FIELD NAME="errorratio" TYPE="number" LENGTH="15" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" DECIMALS="10" PREVIOUS="cic" NEXT="standarderror"/>
+        <FIELD NAME="standarderror" TYPE="number" LENGTH="15" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" DECIMALS="10" PREVIOUS="errorratio"/>
+      </FIELDS>
+      <KEYS>
+        <KEY NAME="primary" TYPE="primary" FIELDS="id"/>
+      </KEYS>
+    </TABLE>
+    <TABLE NAME="quiz_question_statistics" COMMENT="Default comment for the table, please edit me" PREVIOUS="quiz_statistics">
+      <FIELDS>
+        <FIELD NAME="id" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="true" ENUM="false" NEXT="quizstatisticsid"/>
+        <FIELD NAME="quizstatisticsid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="false" ENUM="false" PREVIOUS="id" NEXT="questionid"/>
+        <FIELD NAME="questionid" TYPE="int" LENGTH="10" NOTNULL="true" UNSIGNED="true" SEQUENCE="false" ENUM="false" PREVIOUS="quizstatisticsid" NEXT="subquestion"/>
+        <FIELD NAME="subquestion" TYPE="int" LENGTH="4" NOTNULL="true" UNSIGNED="true" SEQUENCE="false" ENUM="false" PREVIOUS="questionid" NEXT="effectiveweight"/>
+        <FIELD NAME="effectiveweight" TYPE="number" LENGTH="15" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" DECIMALS="5" PREVIOUS="subquestion" NEXT="discriminationindex"/>
+        <FIELD NAME="discriminationindex" TYPE="number" LENGTH="15" NOTNULL="false" UNSIGNED="false" SEQUENCE="false" ENUM="false" DECIMALS="5" PREVIOUS="effectiveweight" NEXT="discriminativeefficiency"/>
+        <FIELD NAME="discriminativeefficiency" TYPE="number" LENGTH="15" NOTNULL="false" UNSIGNED="false" SEQUENCE="false" ENUM="false" DECIMALS="5" PREVIOUS="discriminationindex" NEXT="sd"/>
+        <FIELD NAME="sd" TYPE="number" LENGTH="15" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" DECIMALS="10" PREVIOUS="discriminativeefficiency" NEXT="facility"/>
+        <FIELD NAME="facility" TYPE="number" LENGTH="15" NOTNULL="false" UNSIGNED="true" SEQUENCE="false" ENUM="false" DECIMALS="10" PREVIOUS="sd" NEXT="subquestions"/>
+        <FIELD NAME="subquestions" TYPE="text" LENGTH="medium" NOTNULL="false" SEQUENCE="false" ENUM="false" PREVIOUS="facility"/>
+      </FIELDS>
+      <KEYS>
+        <KEY NAME="primary" TYPE="primary" FIELDS="id"/>
+      </KEYS>
+    </TABLE>
+  </TABLES>
+</XMLDB>
@@ -13,6 +13,7 @@ class qstats{
    function qstats($questions, $s, $sumgradesavg){
        $this->s = $s;
        $this->sumgradesavg = $sumgradesavg;
+        
        foreach (array_keys($questions) as $qid){
            $questions[$qid]->_stats = $this->stats_init_object();
        }
@@ -27,13 +28,16 @@ class qstats{
        $statsinit->othergradevariancesum = 0;
        $statsinit->covariancesum = 0;
        $statsinit->covariancemaxsum = 0;
+        $statsinit->subquestion = false;
+        $statsinit->subquestions = '';
        $statsinit->covariancewithoverallgradesum = 0;
        $statsinit->gradearray = array();
        $statsinit->othergradesarray = array();
        return $statsinit;
    }
-    function get_records($fromqa, $whereqa, $usingattempts, $qaparams){
+    function get_records($quizid, $currentgroup, $groupstudents, $allattempts){
        global $DB;
+        list($fromqa, $whereqa, $qaparams) = quiz_report_attempts_sql($quizid, $currentgroup, $groupstudents, $allattempts);
        $sql = 'SELECT qs.id, ' .
            'qs.question, ' .
            'qa.sumgrades, ' .
@@ -45,7 +49,6 @@ class qstats{
            $fromqa.' '.
            'WHERE ' .$whereqa.
            'AND qns.attemptid = qa.uniqueid '.
-            $usingattempts.
            'AND qns.newgraded = qs.id';
        $this->states = $DB->get_records_sql($sql, $qaparams);
        if ($this->states === false){
@@ -103,12 +106,12 @@ class qstats{
            $stats->discriminationindex = 100*$stats->covariance 
                        / sqrt($stats->gradevariance * $stats->othergradevariance);
        } else {
-            $stats->discriminationindex = '';
+            $stats->discriminationindex = null;
        }
        if ($stats->covariancemax){
            $stats->discriminativeefficiency = 100*$stats->covariance / $stats->covariancemax;
        } else {
-            $stats->discriminativeefficiency = '';
+            $stats->discriminativeefficiency = null;
        }
    }
    
@@ -121,6 +124,7 @@ class qstats{
                    if (!isset($subquestionstats[$itemid])){
                        $subquestionstats[$itemid] = $this->stats_init_object();
                        $subquestionstats[$itemid]->usedin = array();
+                        $subquestionstats[$itemid]->subquestion = true;
                        $subquestionstats[$itemid]->differentweights = false;
                        $subquestionstats[$itemid]->maxgrade = $this->questions[$state->question]->maxgrade;
                    } else if ($subquestionstats[$itemid]->maxgrade != $this->questions[$state->question]->maxgrade){
@@ -142,17 +146,32 @@ class qstats{
        $this->subquestions = question_load_questions(array_keys($subquestionstats));
        foreach (array_keys($this->subquestions) as $qid){
            $this->subquestions[$qid]->_stats = $subquestionstats[$qid];
+            $this->subquestions[$qid]->_stats->questionid = $qid;
            $this->subquestions[$qid]->maxgrade = $this->subquestions[$qid]->_stats->maxgrade;
-            $this->subquestions[$qid]->subquestion = true;
            $this->_initial_question_walker($this->subquestions[$qid]->_stats, $this->subquestions[$qid]->_stats->maxgrade);
            if ($subquestionstats[$qid]->differentweights){
                notify(get_string('erroritemappearsmorethanoncewithdifferentweight', 'quiz_statistics', $this->subquestions[$qid]->name));
            }
        }
-        foreach (array_keys($this->questions) as $qid){
+        reset($this->questions);
+        do{
+            list($qid, $question) = each($this->questions);
+            $nextquestion = current($this->questions);
+            $this->questions[$qid]->_stats->questionid = $qid;
            $this->_initial_question_walker($this->questions[$qid]->_stats, $this->questions[$qid]->maxgrade);
-            $this->questions[$qid]->subquestion = false;
-        }
+            if ($question->qtype == 'random'){
+                $randomselectorstring = $question->category.'/'.$question->questiontext;
+                if ($nextquestion){
+                    $nextrandomselectorstring = $nextquestion->category.'/'.$nextquestion->questiontext;
+                    if ($nextquestion->qtype == 'random' && $randomselectorstring == $nextrandomselectorstring){
+                        continue;//next loop iteration
+                    }
+                }
+                if (isset($this->randomselectors[$randomselectorstring])){
+                    $question->_stats->subquestions = join($this->randomselectors[$randomselectorstring], ',');
+                }
+            }
+        } while ($nextquestion);
        //go through the records one more time
        foreach ($this->states as $state){
            $this->_secondary_states_walker($state, $this->questions[$state->question]->_stats);
@@ -6,8 +6,9 @@
 * @author Martin Dougiamas, Jamie Pratt, Tim Hunt and others.
 * @license http://www.gnu.org/copyleft/gpl.html GNU Public License
 * @package quiz
- *//** */
+ **/

+define('QUIZ_REPORT_TIME_TO_CACHE_STATS', MINSECS * 15);
 require_once($CFG->dirroot.'/mod/quiz/report/statistics/statistics_form.php');
 require_once($CFG->dirroot.'/mod/quiz/report/statistics/statistics_table.php');

@@ -27,7 +28,14 @@ class quiz_statistics_report extends quiz_default_report {
        $pageoptions['id'] = $cm->id;
        $pageoptions['q'] = $quiz->id;
        $pageoptions['mode'] = 'statistics';
+        
+        $questions = quiz_report_load_questions($quiz);
+        // Load the question type specific information
+        if (!get_question_options($questions)) {
+            print_error('cannotloadquestion', 'question');
+        }

+        
        $reporturl = new moodle_url($CFG->wwwroot.'/mod/quiz/report.php', $pageoptions);

        $mform = new mod_quiz_report_statistics($reporturl);
@@ -52,13 +60,10 @@ class quiz_statistics_report extends quiz_default_report {
            if (!$groupstudents){
                $nostudentsingroup = true;
            }
+        } else {
+            $groupstudents = array();
        }

-        $questions = quiz_report_load_questions($quiz);
-        // Load the question type specific information
-        if (!get_question_options($questions)) {
-            print_error('cannotloadquestion', 'question');
-        }
        
        $table = new quiz_report_statistics_table();
        $table->is_downloading($download, get_string('reportstatistics','quiz_statistics'),
@@ -77,7 +82,11 @@ class quiz_statistics_report extends quiz_default_report {
            }
        }

-        
+        if (!$table->is_downloading()) {
+            // Print display options
+            $mform->set_data(array('useallattempts' => $useallattempts));
+            $mform->display();
+        }
        // Print information on the number of existing attempts
        if (!$table->is_downloading()) { //do not print notices when downloading
            print_heading(get_string('quizinformation', 'quiz_statistics'));
@@ -100,31 +109,125 @@ class quiz_statistics_report extends quiz_default_report {
            if ($quiz->timeopen && $quiz->timeclose){
                $quizinformationtable->data[] = array(get_string('duration', 'quiz_statistics'), format_time($quiz->timeclose - $quiz->timeopen));
            }
-            print_table($quizinformationtable);
        }
-        if (!$table->is_downloading()) {
-            // Print display options
-            $mform->set_data(array('useallattempts' => $useallattempts));
-            $mform->display();
-        }
-        $fromqa = '{quiz_attempts} qa ';
-        $whereqa = 'quiz = :quizid AND preview=0 AND timefinish !=0 ';
-        $qaparams = array('quizid'=>$quiz->id);
-        if (!empty($currentgroup) && $groupstudents) {
-            list($grpsql, $grpparams) = $DB->get_in_or_equal(array_keys($groupstudents), SQL_PARAMS_NAMED, 'u0000');
-            $whereqa .= ' AND qa.userid '.$grpsql.' ';
-            $qaparams += $grpparams;
-        }
-        $sql = 'SELECT (CASE WHEN attempt=1 THEN 1 ELSE 0 END) AS isfirst, COUNT(1) AS countrecs, SUM(sumgrades) AS total ' .
-                'FROM '.$fromqa.
-                'WHERE ' .$whereqa.
-                'GROUP BY (attempt=1)';

+        $timemodified = time() - QUIZ_REPORT_TIME_TO_CACHE_STATS;
+        $params = array('quizid'=>$quiz->id, 'groupid'=>$currentgroup, 'allattempts'=>$useallattempts, 'timemodified'=>$timemodified);
+        if (!$quizstats = $DB->get_record_select('quiz_statistics', 'quizid = :quizid  AND groupid = :groupid AND allattempts = :allattempts AND timemodified > :timemodified', $params)){
+            list($s, $usingattemptsstring, $quizstats, $qstats) = $this->quiz_stats($nostudentsingroup, $quiz->id, $currentgroup, $groupstudents, $questions, $useallattempts);
+            $toinsert = (object)((array)$quizstats + $params);
+            $toinsert->timemodified = time();
+            $quizstatisticsid = $DB->insert_record('quiz_statistics', $toinsert);
+            foreach ($qstats->questions as $question){
+                $question->_stats->quizstatisticsid = $quizstatisticsid;
+                $DB->insert_record('quiz_question_statistics', $question->_stats, false, true);
+            }
+            foreach ($qstats->subquestions as $subquestion){
+                $subquestion->_stats->quizstatisticsid = $quizstatisticsid;
+                $DB->insert_record('quiz_question_statistics', $subquestion->_stats, false, true);
+            }
+            if (isset($qstats)){
+                $questions = $qstats->questions;
+                $subquestions = $qstats->subquestions;
+            } else {
+                $questions = array();
+                $subquestions = array();
+            }
+        } else {
+            if ($useallattempts){
+                $usingattemptsstring = get_string('allattempts', 'quiz_statistics');
+                $s = $quizstats->allattemptscount;
+            } else {
+                $usingattemptsstring = get_string('firstattempts', 'quiz_statistics');
+                $s = $quizstats->firstattemptscount;
+            }
+            $questionstats = $DB->get_records('quiz_question_statistics', array('quizstatisticsid'=>$quizstats->id), 'subquestion ASC');
+            $questionstats = quiz_report_index_by_keys($questionstats, array('subquestion', 'questionid'));
+            if (1 < count($questionstats)){
+                list($mainquestionstats, $subquestionstats) = $questionstats;
+                $subqstofetch = array_keys($subquestionstats);
+                $subquestions = question_load_questions($subqstofetch);
+                foreach (array_keys($subquestions) as $subqid){
+                    $subquestions[$subqid]->_stats = $subquestionstats[$subqid];
+                }
+            } else {
+                $mainquestionstats = $questionstats[0];
+                $subquestions = array();
+            }
+            foreach (array_keys($questions) as $qid){
+                $questions[$qid]->_stats = $mainquestionstats[$qid];
+            }
+        }
+        if (!$table->is_downloading()){
+            if ($s==0){
+                print_heading(get_string('noattempts','quiz'));
+            }
+            $format = array('firstattemptscount' => '',
+                        'allattemptscount' => '',
+                        'firstattemptsavg' => 'sumgrades_as_percentage',
+                        'allattemptsavg' => 'sumgrades_as_percentage',
+                        'median' => 'sumgrades_as_percentage',
+                        'standarddeviation' => 'sumgrades_as_percentage',
+                        'skewness' => '',
+                        'kurtosis' => '',
+                        'cic' => 'number_format',
+                        'errorratio' => 'number_format',
+                        'standarderror' => 'sumgrades_as_percentage');
+            foreach ($quizstats as $property => $value){
+                if (!isset($format[$property])){
+                    continue;
+                }
+                switch ($format[$property]){
+                    case 'sumgrades_as_percentage' :
+                        $formattedvalue = quiz_report_scale_sumgrades_as_percentage($value, $quiz);
+                        break;
+                    case 'number_format' :
+                        $formattedvalue = number_format($value, $quiz->decimalpoints).' %';
+                        break;
+                    default :
+                        $formattedvalue = $value;
+                }
+                $quizinformationtable->data[] = array(get_string($property, 'quiz_statistics', $usingattemptsstring), $formattedvalue);
+            }
+            print_table($quizinformationtable);
+            
+        }
+        if (!$table->is_downloading()){
+            print_heading(get_string('quizstructureanalysis', 'quiz_statistics'));
+        }
+        if ($s){
+            $table->setup($quiz, $cm->id, $reporturl, $s);
+            
+            foreach ($questions as $question){
+                $table->add_data_keyed($table->format_row($question));
+                if (!empty($question->_stats->subquestions)){
+                    $subitemstodisplay = explode(',', $question->_stats->subquestions);
+                    foreach ($subitemstodisplay as $subitemid){
+                        $subquestions[$subitemid]->maxgrade = $question->maxgrade;
+                        $table->add_data_keyed($table->format_row($subquestions[$subitemid]));
+                    }
+                }
+            }
+
+            $table->finish_output();
+        }
+        return true;
+    }
+    
+    
+    function quiz_stats($nostudentsingroup, $quizid, $currentgroup, $groupstudents, $questions, $useallattempts){
+        global $CFG, $DB;
        if (!$nostudentsingroup){
            //Calculating_MEAN_of_grades_for_all_attempts_by_students
            //http://docs.moodle.org/en/Development:Quiz_item_analysis_calculations_in_practise#Calculating_MEAN_of_grades_for_all_attempts_by_students
+        
+            list($fromqa, $whereqa, $qaparams) = quiz_report_attempts_sql($quizid, $currentgroup, $groupstudents);
+    
+            $sql = 'SELECT (CASE WHEN attempt=1 THEN 1 ELSE 0 END) AS isfirst, COUNT(1) AS countrecs, SUM(sumgrades) AS total ' .
+                    'FROM '.$fromqa.
+                    'WHERE ' .$whereqa.
+                    'GROUP BY (attempt=1)';
            if (!$attempttotals = $DB->get_records_sql($sql, $qaparams)){
-                print_heading(get_string('noattempts','quiz'));
                $s = 0;
            } else {
                $firstattempt = $attempttotals[1];
@@ -142,61 +245,52 @@ class quiz_statistics_report extends quiz_default_report {
                    $usingattempts->attempts = get_string('firstattempts', 'quiz_statistics');
                    $usingattempts->sql = 'AND qa.attempt=1 ';
                }
-                $usingattempts->heading = get_string('statsfor', 'quiz_statistics', $usingattempts->attempts);
+                $usingattemptsstring = $usingattempts->attempts;
                $s = $usingattempts->countrecs;
                $sumgradesavg = $usingattempts->total / $usingattempts->countrecs;
            }
        } else {
            $s = 0;
        }
-       
-        if ($s && !$table->is_downloading()) {
-            print_heading(get_string('quizoverallstatistics', 'quiz_statistics'));
-            $quizoverallstatistics = new object();
-            $quizoverallstatistics->align = array('center', 'center');
-            $quizoverallstatistics->width = '60%';
-            $quizoverallstatistics->class = 'generaltable titlesleft';
-            $quizoverallstatistics->data = array();
-            $quizoverallstatistics->data[] = array(get_string('nooffirstattempts', 'quiz_statistics'), $firstattempt->countrecs);
-            $quizoverallstatistics->data[] = array(get_string('noofallattempts', 'quiz_statistics'), $allattempts->countrecs);
-            $quizoverallstatistics->data[] = array(get_string('firstattemptsavg', 'quiz_statistics'), quiz_report_scale_sumgrades_as_percentage($firstattempt->total / $firstattempt->countrecs, $quiz));
-            $quizoverallstatistics->data[] = array(get_string('allattemptsavg', 'quiz_statistics'), quiz_report_scale_sumgrades_as_percentage($allattempts->total / $allattempts->countrecs, $quiz));
-            print_table($quizoverallstatistics);
+        $quizstats = new object();
+        if ($s == 0){
+            $quizstats->firstattemptscount = 0;
+            $quizstats->allattemptscount = 0;
+        } else {
+            $quizstats->firstattemptscount = $firstattempt->countrecs;
+            $quizstats->allattemptscount = $allattempts->countrecs;
+            $quizstats->firstattemptsavg = $firstattempt->total / $firstattempt->countrecs;
+            $quizstats->allattemptsavg = $allattempts->total / $allattempts->countrecs;
        }
-        $quizattsstatistics = new object();
-        $quizattsstatistics->align = array('center', 'center');
-        $quizattsstatistics->width = '60%';
-        $quizattsstatistics->class = 'generaltable titlesleft';
-        $quizattsstatistics->data = array();
+        //recalculate sql again this time possibly including test for first attempt.
+        list($fromqa, $whereqa, $qaparams) = quiz_report_attempts_sql($quizid, $currentgroup, $groupstudents, $useallattempts);
+        
        //get the median
-        if ($s && !$table->is_downloading()) {
+        if ($s) {

-            print_heading($usingattempts->heading);
            if (($s%2)==0){
                //even number of attempts
                $limitoffset = ($s/2) - 1;
                $limit = 2;
            } else {
-                $limitoffset = (floor($s/2)) - 1;
+                $limitoffset = (floor($s/2)) + 1;
                $limit = 1;
            }
            $sql = 'SELECT id, sumgrades ' .
                'FROM ' .$fromqa.
                'WHERE ' .$whereqa.
-                $usingattempts->sql.
                'ORDER BY sumgrades';
            if (!$mediangrades = $DB->get_records_sql_menu($sql, $qaparams, $limitoffset, $limit)){
                print_error('errormedian', 'quiz_statistics');
            }
            if (count($mediangrades)==1){
-                $median = array_shift($mediangrades);
+                $quizstats->median = array_shift($mediangrades);
            } else {
                $median = array_shift($mediangrades);
                $median += array_shift($mediangrades);
-                $median = $median /2;
+                $quizstats->median = $median /2;
            }
            if ($s>1){
-                $quizattsstatistics->data[] = array(get_string('median', 'quiz_statistics'), quiz_report_scale_sumgrades_as_percentage($median, $quiz));
                //fetch sum of squared, cubed and power 4d 
                //differences between grades and mean grade
                $mean = $usingattempts->total / $s;
@@ -205,8 +299,7 @@ class quiz_statistics_report extends quiz_default_report {
                    "SUM(POWER((qa.sumgrades - :mean2),3)) AS power3, ".
                    "SUM(POWER((qa.sumgrades - :mean3),4)) AS power4 ".
                    'FROM ' .$fromqa.
-                    'WHERE ' .$whereqa.
-                    $usingattempts->sql;
+                    'WHERE ' .$whereqa;
                $params = array('mean1' => $mean, 'mean2' => $mean, 'mean3' => $mean)+$qaparams;
                if (!$powers = $DB->get_record_sql($sql, $params)){
                    print_error('errorpowers', 'quiz_statistics');
@@ -215,8 +308,8 @@ class quiz_statistics_report extends quiz_default_report {
                //Standard_Deviation
                //see http://docs.moodle.org/en/Development:Quiz_item_analysis_calculations_in_practise#Standard_Deviation
                
-                $sd = sqrt($powers->power2 / ($s -1));
-                $quizattsstatistics->data[] = array(get_string('standarddeviation', 'quiz_statistics'), quiz_report_scale_sumgrades_as_percentage($sd, $quiz));
+                $quizstats->standarddeviation = sqrt($powers->power2 / ($s -1));
+                

                
                //Skewness_and_Kurtosis
@@ -229,73 +322,51 @@ class quiz_statistics_report extends quiz_default_report {
                    $k2= $s*$m2/($s-1);
                    $k3= $s*$s*$m3/(($s-1)*($s-2));
                    
-                    $skewness = $k3 / (pow($k2, 2/3));
-                    $quizattsstatistics->data[] = array(get_string('skewness', 'quiz_statistics'), $skewness);
+                    $quizstats->skewness = $k3 / (pow($k2, 2/3));
                }
    
    
                if ($s>3){
                    $k4= (($s*$s*$s)/(($s-1)*($s-2)*($s-3)))*((($s+1)*$m4)-(3*($s-1)*$m2*$m2));
                    
-                    $kurtosis = $k4 / ($k2*$k2);
-                    
-                    $quizattsstatistics->data[] = array(get_string('kurtosis', 'quiz_statistics'), $kurtosis);
+                    $quizstats->kurtosis = $k4 / ($k2*$k2);
                }
            }
        }
        if ($s){
            require_once("$CFG->dirroot/mod/quiz/report/statistics/qstats.php");
            $qstats = new qstats($questions, $s, $sumgradesavg);
-            $qstats->get_records($fromqa, $whereqa, $usingattempts->sql, $qaparams);
+            $qstats->get_records($quizid, $currentgroup, $groupstudents, $useallattempts);
            set_time_limit(0);
            $qstats->process_states();
+        } else {
+            $qstats = false;
        }
-        if (!$table->is_downloading()){
-            if ($s>1){
-                $p = count($questions);//no of positions
-                if ($p > 1){
-                    $cic = (100 * $p / ($p -1)) * (1 - ($qstats->sum_of_grade_variance())/$k2);
-                    $quizattsstatistics->data[] = array(get_string('cic', 'quiz_statistics'), number_format($cic, $quiz->decimalpoints).' %');
-                    $errorratio = 100 * sqrt(1-($cic/100));
-                    $quizattsstatistics->data[] = array(get_string('errorratio', 'quiz_statistics'), number_format($errorratio, $quiz->decimalpoints).' %');
-                    $standarderror = ($errorratio * $sd / 100);
-                    $quizattsstatistics->data[] = array(get_string('standarderror', 'quiz_statistics'), 
-                        quiz_report_scale_sumgrades_as_percentage($standarderror, $quiz));
-                }
-            }
-            if ($quizattsstatistics->data){
-                print_table($quizattsstatistics);
+        if ($s>1){
+            $p = count($qstats->questions);//no of positions
+            if ($p > 1){
+                $quizstats->cic = (100 * $p / ($p -1)) * (1 - ($qstats->sum_of_grade_variance())/$k2);
+                $quizstats->errorratio = 100 * sqrt(1-($quizstats->cic/100));
+                $quizstats->standarderror = ($quizstats->errorratio * $quizstats->standarddeviation / 100);
+                
            }
        }
-        if (!$table->is_downloading()){
-            print_heading(get_string('quizstructureanalysis', 'quiz_statistics'));
-        }
-        $table->setup($quiz, $cm->id, $reporturl, $s);
-        if (isset($qstats)){
-            while ($question = array_shift($qstats->questions)){
-                $table->add_data_keyed($table->format_row($question));
-                if ($question->qtype == 'random'){
-                    $randomselectorstring = $question->category.'/'.$question->questiontext;
-                    if ($qstats->questions){
-                        $nextquestion = current($qstats->questions);
-                        $nextrandomselectorstring = $nextquestion->category.'/'.$nextquestion->questiontext;
-                        if ($nextquestion->qtype == 'random' && $randomselectorstring == $nextrandomselectorstring){
-                            continue;//next loop iteration
-                        }
-                    }
-                    if (isset($qstats->randomselectors[$randomselectorstring])){
-                        foreach ($qstats->randomselectors[$randomselectorstring] as $itemid){
-                            $table->add_data_keyed($table->format_row($qstats->subquestions[$itemid]));
-                        }
-                    }
-                }
-            }
-        }
-        $table->finish_output();
-        return true;
+        return array($s, $usingattemptsstring, $quizstats, $qstats);
    }

 }
-
-
+function quiz_report_attempts_sql($quizid, $currentgroup, $groupstudents, $allattempts = true){
+    $fromqa = '{quiz_attempts} qa ';
+    $whereqa = 'quiz = :quizid AND preview=0 AND timefinish !=0 ';
+    $qaparams = array('quizid'=>$quizid);
+    if (!empty($currentgroup) && $groupstudents) {
+        list($grpsql, $grpparams) = $DB->get_in_or_equal(array_keys($groupstudents), SQL_PARAMS_NAMED, 'u0000');
+        $whereqa .= 'AND qa.userid '.$grpsql.' ';
+        $qaparams += $grpparams;
+    }
+    if (!$allattempts){
+        $whereqa .= 'AND qa.attempt=1 ';
+    }
+    return array($fromqa, $whereqa, $qaparams);
+}
 ?>
@@ -43,7 +43,7 @@ class quiz_report_statistics_table extends flexible_table {
            $headers[]= get_string('facility', 'quiz_statistics');
            
            $columns[]= 'sd';
-            $headers[]= get_string('standarddeviation', 'quiz_statistics');
+            $headers[]= get_string('standarddeviationq', 'quiz_statistics');
        }
        $columns[]= 'random_guess_score';
        $headers[]= get_string('random_guess_score', 'quiz_statistics');
@@ -108,7 +108,7 @@ class quiz_report_statistics_table extends flexible_table {
    }
    
    function col_number($question){
-        if (!$question->subquestion){
+        if (!$question->_stats->subquestion){
            return $question->number;
        } else {
            return '';
@@ -124,7 +124,7 @@ class quiz_report_statistics_table extends flexible_table {
        return quiz_report_scale_sumgrades_as_percentage($question->maxgrade, $this->quiz);
    }
    function col_effective_weight($question){
-        if (!$question->subquestion){
+        if (!$question->_stats->subquestion){
            return number_format($question->_stats->effectiveweight, 2).' %';
        } else {
            return '';
@@ -0,0 +1,4 @@
+<?php
+$plugin->version  = 2008072400;   // The (date) version of this module
+
+?>