[moodle.git] / mod / quiz / report / statistics / report.php

<?php
/**
 * This script lists student attempts
 *
 * @version $Id$
 * @author Martin Dougiamas, Tim Hunt and others.
 * @license http://www.gnu.org/copyleft/gpl.html GNU Public License
 * @package quiz
 *//** */

require_once($CFG->libdir.'/tablelib.php');
require_once($CFG->dirroot.'/mod/quiz/report/statistics/statistics_form.php');
require_once($CFG->dirroot.'/mod/quiz/report/statistics/statistics_table.php');

class quiz_report extends quiz_default_report {

    /**
     * Display the report.
     */
    function display($quiz, $cm, $course) {
        global $CFG, $DB;

        $context = get_context_instance(CONTEXT_MODULE, $cm->id);

        $download = optional_param('download', '', PARAM_ALPHA);

        $pageoptions = array();
        $pageoptions['id'] = $cm->id;
        $pageoptions['q'] = $quiz->id;
        $pageoptions['mode'] = 'statistics';

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

        $mform = new mod_quiz_report_statistics($reporturl);
        if ($fromform = $mform->get_data()){
            $useallattempts = $fromform->useallattempts;
            if ($fromform->useallattempts){
                set_user_preference('quiz_report_statistics_useallattempts', $fromform->useallattempts);
            } else {
                unset_user_preference('quiz_report_statistics_useallattempts');
            }
        } else {
            $useallattempts = get_user_preferences('quiz_report_statistics_useallattempts', 0);
        }

        /// find out current groups mode
        $currentgroup = groups_get_activity_group($cm, true);

        if (!empty($currentgroup)) {
            // all users who can attempt quizzes and who are in the currently selected group
            if (!$groupstudents = get_users_by_capability($context, 'mod/quiz:attempt','','','','',$currentgroup,'',false)){
                $groupstudents = array();
            }
            $groupstudentslist = join(',', array_keys($groupstudents));
            $allowedlist = $groupstudentslist;
        }

        $questions = question_load_questions(quiz_questions_in_quiz($quiz->questions));

        $table = new quiz_report_statistics_table();
        $table->is_downloading($download, get_string('reportstatistics','quiz_statistics'),
                    "$course->shortname ".format_string($quiz->name,true));
        if (!$table->is_downloading()) {
            // Only print headers if not asked to download data
            $this->print_header_and_tabs($cm, $course, $quiz, "statistics");
        }

        if ($groupmode = groups_get_activity_groupmode($cm)) {   // Groups are being used
            if (!$table->is_downloading()) {
                groups_print_activity_menu($cm, $reporturl->out());
            }
        }

        
        // 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'));
            $quizinformationtable = new object();
            $quizinformationtable->align = array('center', 'center');
            $quizinformationtable->width = '60%';
            $quizinformationtable->class = 'generaltable titlesleft';
            $quizinformationtable->data = array();
            $quizinformationtable->data[] = array(get_string('quizname', 'quiz_statistics'), $quiz->name);
            $quizinformationtable->data[] = array(get_string('coursename', 'quiz_statistics'), $course->fullname);
            if ($cm->idnumber){
                $quizinformationtable->data[] = array(get_string('coursename', 'quiz_statistics'), $cm->idnumber);
            }
            if ($quiz->timeopen){
                $quizinformationtable->data[] = array(get_string('quizopen', 'quiz'), userdate($quiz->timeopen));
            }
            if ($quiz->timeclose){
                $quizinformationtable->data[] = array(get_string('quizclose', 'quiz'), userdate($quiz->timeclose));
            }
            if ($quiz->timeopen && $quiz->timeclose){
                $quizinformationtable->data[] = array(get_string('duration'), format_time($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 = ? AND preview=0 AND timefinish !=0 ';
        $sql = 'SELECT (attempt=1) AS isfirst, COUNT(1) AS countrecs, SUM(sumgrades) AS total ' .
                'FROM '.$fromqa.
                'WHERE ' .$whereqa.
                'GROUP BY (attempt=1)';

        //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
        if (!$attempttotals = $DB->get_records_sql($sql, array($quiz->id))){
            print_heading(get_string('noattempts','quiz'));
            return true;
        } else {
            $firstattempt = $attempttotals[1];
            $allattempts = new object();
            $allattempts->countrecs = $firstattempt->countrecs + 
                            (isset($attempttotals[0])?$attempttotals[0]->countrecs:0);
            $allattempts->total = $firstattempt->total + 
                            (isset($attempttotals[0])?$attempttotals[0]->total:0);
        }
        
        if (!$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);
        }
        //get the median
        if (!$table->is_downloading()) {
            if ($useallattempts){
                $usingattempts = $allattempts;
                $usingattempts->heading = get_string('statsforallattempts', 'quiz_statistics');
                $usingattempts->sql = '';
            } else {
                $usingattempts = $firstattempt;
                $usingattempts->heading = get_string('statsforfirstattempts', 'quiz_statistics');
                $usingattempts->sql = 'AND qa.attempt=1 ';
            }
            print_heading($usingattempts->heading);
            if (($usingattempts->countrecs/2)==floor($usingattempts->countrecs/2)){
                //even number of attempts
                $limitoffset = (floor($usingattempts->countrecs/2)) - 1;
                $limit = 2;
            } else {
                $limitoffset = ($usingattempts->countrecs/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, array($quiz->id), $limitoffset, $limit)){
                print_error('errormedian', 'quiz_statistics');
            }
            if (count($mediangrades)==1){
                $median = array_shift($mediangrades);
            } else {
                $median = array_shift($mediangrades);
                $median += array_shift($mediangrades);
                $median = $median /2;
            }
            //fetch sum of squared, cubed and power 4d 
            //differences between grades and mean grade
            $mean = $usingattempts->total / $usingattempts->countrecs;
            $sql = "SELECT " .
                "SUM(POWER((qa.sumgrades - ?),2)) AS power2, " .
                "SUM(POWER((qa.sumgrades - ?),3)) AS power3, ".
                "SUM(POWER((qa.sumgrades - ?),4)) AS power4 ".
                'FROM ' .$fromqa.
                'WHERE ' .$whereqa.
                $usingattempts->sql;
            $params = array($mean, $mean, $mean, $quiz->id);
            if (!$powers = $DB->get_record_sql($sql, $params)){
                print_error('errorpowers', 'quiz_statistics');
            }
            
            $s = $usingattempts->countrecs;
            
            //Standard_Deviation
            //see http://docs.moodle.org/en/Development:Quiz_item_analysis_calculations_in_practise#Standard_Deviation
            
            $sd = sqrt($powers->power2 / ($s -1));
            
            //Skewness_and_Kurtosis
            //see http://docs.moodle.org/en/Development:Quiz_item_analysis_calculations_in_practise#Skewness_and_Kurtosis
            $m2= $powers->power2 / $s;
            $m3= $powers->power3 / $s;
            $m4= $powers->power4 / $s;
            
            $k2= $s*$m2/($s-1);
            $k3= $s*$s*$m3/(($s-1)*($s-2));
            $k4= (($s*$s*$s)/(($s-1)*($s-2)*($s-3)))*((($s+1)*$m4)-(3*($s-1)*$m2*$m2));
            
            $skewness = $k3 / (pow($k2, 2/3));
            $kurtosis = $k4 / ($k2*$k2);
            
            $quizattsstatistics = new object();
            $quizattsstatistics->align = array('center', 'center');
            $quizattsstatistics->width = '60%';
            $quizattsstatistics->class = 'generaltable titlesleft';
            $quizattsstatistics->data = array();
            
            $quizattsstatistics->data[] = array(get_string('median', 'quiz_statistics'), quiz_report_scale_sumgrades_as_percentage($median, $quiz));
            $quizattsstatistics->data[] = array(get_string('standarddeviation', 'quiz_statistics'), quiz_report_scale_sumgrades_as_percentage($sd, $quiz));
            $quizattsstatistics->data[] = array(get_string('skewness', 'quiz_statistics'), $skewness);
            $quizattsstatistics->data[] = array(get_string('kurtosis', 'quiz_statistics'), $kurtosis);

            //CIC, ER and SE.
            //http://docs.moodle.org/en/Development:Quiz_item_analysis_calculations_in_practise#CIC.2C_ER_and_SE
            $qgradeavgsql = "SELECT qs.question, AVG(qs.grade) FROM " .
                    "{question_sessions} qns, " .
                    "{question_states} qs, " .
                    "{question} q, " .
                    $fromqa.' '.
                    'WHERE ' .$whereqa.
                    'AND qns.attemptid = qa.uniqueid '.
                    'AND qs.question = q.id ' .
                    'AND q.length > 0 '.
                    $usingattempts->sql.
                    'AND qns.newgraded = qs.id GROUP BY qs.question';
            $qgradeavgs = $DB->get_records_sql_menu($qgradeavgsql, array($quiz->id));
            $sum = 0;
            $sql = 'SELECT ' .
                    'SUM(POWER((qs.grade - ?),2)) AS power2 ' .
                    'FROM ' .
                    '{question_sessions} qns, ' .
                    '{question_states} qs, ' .
                    '{question} q, ' .
                    $fromqa.' '.
                    'WHERE ' .$whereqa.
                    'AND qns.attemptid = qa.uniqueid '.
                    'AND qs.question = ? ' .
                    $usingattempts->sql.
                    'AND qns.newgraded = qs.id';
            foreach ($qgradeavgs as $qid => $qgradeavg){
                $params = array($qgradeavg, $quiz->id, $qid);
                $power = $DB->get_field_sql($sql, $params);
                if ($power === false){
                    print_error('errorpowerquestions', 'quiz_statistics');
                }
                $sum += $power;
            }
            $sumofvarianceforallpositions = $sum / ($usingattempts->countrecs -1);
            $p = count($qgradeavgs);//no of positions
            $cic = (100 * $p / ($p -1)) * (1 - ($sumofvarianceforallpositions/$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, $quiz));
            print_table($quizattsstatistics);
            
        }
        if (!$table->is_downloading()){
            print_heading(get_string('quizstructureanalysis', 'quiz_statistics'));
        }
        $table->setup($quiz, $cm->id, $reporturl);
        foreach ($questions as $question){
            $table->add_data_keyed($table->format_row($question));
        }
        $table->finish_output();
        return true;
    }

}


?>
Commit	Line	Data
0c1c764e	1	<?php
	2	/**
	3	* This script lists student attempts
	4	*
	5	* @version $Id$
	6	* @author Martin Dougiamas, Tim Hunt and others.
	7	* @license http://www.gnu.org/copyleft/gpl.html GNU Public License
	8	* @package quiz
	9	//* */
	10
	11	require_once($CFG->libdir.'/tablelib.php');
	12	require_once($CFG->dirroot.'/mod/quiz/report/statistics/statistics_form.php');
	13	require_once($CFG->dirroot.'/mod/quiz/report/statistics/statistics_table.php');
	14
	15	class quiz_report extends quiz_default_report {
	16
	17	/**
	18	* Display the report.
	19	*/
	20	function display($quiz, $cm, $course) {
	21	global $CFG, $DB;
	22
	23	$context = get_context_instance(CONTEXT_MODULE, $cm->id);
	24
	25	$download = optional_param('download', '', PARAM_ALPHA);
	26
	27	$pageoptions = array();
	28	$pageoptions['id'] = $cm->id;
	29	$pageoptions['q'] = $quiz->id;
	30	$pageoptions['mode'] = 'statistics';
	31
	32	$reporturl = new moodle_url($CFG->wwwroot.'/mod/quiz/report.php', $pageoptions);
	33
	34	$mform = new mod_quiz_report_statistics($reporturl);
	35	if ($fromform = $mform->get_data()){
	36	$useallattempts = $fromform->useallattempts;
	37	if ($fromform->useallattempts){
	38	set_user_preference('quiz_report_statistics_useallattempts', $fromform->useallattempts);
	39	} else {
	40	unset_user_preference('quiz_report_statistics_useallattempts');
	41	}
	42	} else {
	43	$useallattempts = get_user_preferences('quiz_report_statistics_useallattempts', 0);
	44	}
	45
	46	/// find out current groups mode
	47	$currentgroup = groups_get_activity_group($cm, true);
	48
	49	if (!empty($currentgroup)) {
	50	// all users who can attempt quizzes and who are in the currently selected group
	51	if (!$groupstudents = get_users_by_capability($context, 'mod/quiz:attempt','','','','',$currentgroup,'',false)){
	52	$groupstudents = array();
	53	}
	54	$groupstudentslist = join(',', array_keys($groupstudents));
	55	$allowedlist = $groupstudentslist;
	56	}
	57
c0250840	58	$questions = question_load_questions(quiz_questions_in_quiz($quiz->questions));
0c1c764e	59
c0250840	60	$table = new quiz_report_statistics_table();
0c1c764e	61	$table->is_downloading($download, get_string('reportstatistics','quiz_statistics'),
	62	"$course->shortname ".format_string($quiz->name,true));
	63	if (!$table->is_downloading()) {
	64	// Only print headers if not asked to download data
	65	$this->print_header_and_tabs($cm, $course, $quiz, "statistics");
	66	}
	67
	68	if ($groupmode = groups_get_activity_groupmode($cm)) { // Groups are being used
	69	if (!$table->is_downloading()) {
	70	groups_print_activity_menu($cm, $reporturl->out());
	71	}
	72	}
	73
	74
	75	// Print information on the number of existing attempts
	76	if (!$table->is_downloading()) { //do not print notices when downloading
	77	print_heading(get_string('quizinformation', 'quiz_statistics'));
	78	$quizinformationtable = new object();
	79	$quizinformationtable->align = array('center', 'center');
	80	$quizinformationtable->width = '60%';
	81	$quizinformationtable->class = 'generaltable titlesleft';
	82	$quizinformationtable->data = array();
	83	$quizinformationtable->data[] = array(get_string('quizname', 'quiz_statistics'), $quiz->name);
	84	$quizinformationtable->data[] = array(get_string('coursename', 'quiz_statistics'), $course->fullname);
	85	if ($cm->idnumber){
	86	$quizinformationtable->data[] = array(get_string('coursename', 'quiz_statistics'), $cm->idnumber);
	87	}
	88	if ($quiz->timeopen){
	89	$quizinformationtable->data[] = array(get_string('quizopen', 'quiz'), userdate($quiz->timeopen));
	90	}
	91	if ($quiz->timeclose){
	92	$quizinformationtable->data[] = array(get_string('quizclose', 'quiz'), userdate($quiz->timeclose));
	93	}
	94	if ($quiz->timeopen && $quiz->timeclose){
	95	$quizinformationtable->data[] = array(get_string('duration'), format_time($quiz->timeclose - $quiz->timeopen));
	96	}
	97	print_table($quizinformationtable);
	98	}
	99	if (!$table->is_downloading()) {
	100	// Print display options
	101	$mform->set_data(array('useallattempts' => $useallattempts));
	102	$mform->display();
	103	}
08a7ead5	104	$fromqa = '{quiz_attempts} qa ';
08a7ead5	105	$whereqa = 'quiz = ? AND preview=0 AND timefinish !=0 ';
0c1c764e	106	$sql = 'SELECT (attempt=1) AS isfirst, COUNT(1) AS countrecs, SUM(sumgrades) AS total ' .
08a7ead5	107	'FROM '.$fromqa.
08a7ead5	108	'WHERE ' .$whereqa.
0c1c764e	109	'GROUP BY (attempt=1)';
0c1c764e	110
040c36e3	111	//Calculating_MEAN_of_grades_for_all_attempts_by_students
040c36e3	112	//http://docs.moodle.org/en/Development:Quiz_item_analysis_calculations_in_practise#Calculating_MEAN_of_grades_for_all_attempts_by_students
08a7ead5	113	if (!$attempttotals = $DB->get_records_sql($sql, array($quiz->id))){
0c1c764e	114	print_heading(get_string('noattempts','quiz'));
	115	return true;
	116	} else {
	117	$firstattempt = $attempttotals[1];
	118	$allattempts = new object();
	119	$allattempts->countrecs = $firstattempt->countrecs +
	120	(isset($attempttotals[0])?$attempttotals[0]->countrecs:0);
	121	$allattempts->total = $firstattempt->total +
	122	(isset($attempttotals[0])?$attempttotals[0]->total:0);
	123	}
	124
	125	if (!$table->is_downloading()) {
	126	print_heading(get_string('quizoverallstatistics', 'quiz_statistics'));
	127	$quizoverallstatistics = new object();
	128	$quizoverallstatistics->align = array('center', 'center');
	129	$quizoverallstatistics->width = '60%';
	130	$quizoverallstatistics->class = 'generaltable titlesleft';
	131	$quizoverallstatistics->data = array();
	132	$quizoverallstatistics->data[] = array(get_string('nooffirstattempts', 'quiz_statistics'), $firstattempt->countrecs);
	133	$quizoverallstatistics->data[] = array(get_string('noofallattempts', 'quiz_statistics'), $allattempts->countrecs);
	134	$quizoverallstatistics->data[] = array(get_string('firstattemptsavg', 'quiz_statistics'), quiz_report_scale_sumgrades_as_percentage($firstattempt->total / $firstattempt->countrecs, $quiz));
	135	$quizoverallstatistics->data[] = array(get_string('allattemptsavg', 'quiz_statistics'), quiz_report_scale_sumgrades_as_percentage($allattempts->total / $allattempts->countrecs, $quiz));
	136	print_table($quizoverallstatistics);
	137	}
	138	//get the median
0c1c764e	139	if (!$table->is_downloading()) {
	140	if ($useallattempts){
	141	$usingattempts = $allattempts;
	142	$usingattempts->heading = get_string('statsforallattempts', 'quiz_statistics');
	143	$usingattempts->sql = '';
	144	} else {
	145	$usingattempts = $firstattempt;
	146	$usingattempts->heading = get_string('statsforfirstattempts', 'quiz_statistics');
08a7ead5	147	$usingattempts->sql = 'AND qa.attempt=1 ';
0c1c764e	148	}
	149	print_heading($usingattempts->heading);
	150	if (($usingattempts->countrecs/2)==floor($usingattempts->countrecs/2)){
	151	//even number of attempts
	152	$limitoffset = (floor($usingattempts->countrecs/2)) - 1;
	153	$limit = 2;
	154	} else {
	155	$limitoffset = ($usingattempts->countrecs/2) - 1;
	156	$limit = 1;
	157	}
	158	$sql = 'SELECT id, sumgrades ' .
08a7ead5	159	'FROM ' .$fromqa.
08a7ead5	160	'WHERE ' .$whereqa.
0c1c764e	161	$usingattempts->sql.
0c1c764e	162	'ORDER BY sumgrades';
08a7ead5	163	if (!$mediangrades = $DB->get_records_sql_menu($sql, array($quiz->id), $limitoffset, $limit)){
0c1c764e	164	print_error('errormedian', 'quiz_statistics');
	165	}
	166	if (count($mediangrades)==1){
	167	$median = array_shift($mediangrades);
	168	} else {
	169	$median = array_shift($mediangrades);
	170	$median += array_shift($mediangrades);
	171	$median = $median /2;
	172	}
	173	//fetch sum of squared, cubed and power 4d
	174	//differences between grades and mean grade
	175	$mean = $usingattempts->total / $usingattempts->countrecs;
	176	$sql = "SELECT " .
08a7ead5	177	"SUM(POWER((qa.sumgrades - ?),2)) AS power2, " .
	178	"SUM(POWER((qa.sumgrades - ?),3)) AS power3, ".
	179	"SUM(POWER((qa.sumgrades - ?),4)) AS power4 ".
	180	'FROM ' .$fromqa.
	181	'WHERE ' .$whereqa.
	182	$usingattempts->sql;
0c1c764e	183	$params = array($mean, $mean, $mean, $quiz->id);
	184	if (!$powers = $DB->get_record_sql($sql, $params)){
	185	print_error('errorpowers', 'quiz_statistics');
	186	}
	187
	188	$s = $usingattempts->countrecs;
	189
040c36e3	190	//Standard_Deviation
	191	//see http://docs.moodle.org/en/Development:Quiz_item_analysis_calculations_in_practise#Standard_Deviation
	192
0c1c764e	193	$sd = sqrt($powers->power2 / ($s -1));
0c1c764e	194
040c36e3	195	//Skewness_and_Kurtosis
040c36e3	196	//see http://docs.moodle.org/en/Development:Quiz_item_analysis_calculations_in_practise#Skewness_and_Kurtosis
0c1c764e	197	$m2= $powers->power2 / $s;
	198	$m3= $powers->power3 / $s;
	199	$m4= $powers->power4 / $s;
	200
	201	$k2= $s*$m2/($s-1);
	202	$k3= $s$s$m3/(($s-1)*($s-2));
040c36e3	203	$k4= (($s$s$s)/(($s-1)($s-2)($s-3)))((($s+1)$m4)-(3($s-1)$m2*$m2));
0c1c764e	204
	205	$skewness = $k3 / (pow($k2, 2/3));
	206	$kurtosis = $k4 / ($k2*$k2);
	207
	208	$quizattsstatistics = new object();
	209	$quizattsstatistics->align = array('center', 'center');
	210	$quizattsstatistics->width = '60%';
	211	$quizattsstatistics->class = 'generaltable titlesleft';
	212	$quizattsstatistics->data = array();
	213
	214	$quizattsstatistics->data[] = array(get_string('median', 'quiz_statistics'), quiz_report_scale_sumgrades_as_percentage($median, $quiz));
	215	$quizattsstatistics->data[] = array(get_string('standarddeviation', 'quiz_statistics'), quiz_report_scale_sumgrades_as_percentage($sd, $quiz));
	216	$quizattsstatistics->data[] = array(get_string('skewness', 'quiz_statistics'), $skewness);
	217	$quizattsstatistics->data[] = array(get_string('kurtosis', 'quiz_statistics'), $kurtosis);
08a7ead5	218
040c36e3	219	//CIC, ER and SE.
040c36e3	220	//http://docs.moodle.org/en/Development:Quiz_item_analysis_calculations_in_practise#CIC.2C_ER_and_SE
08a7ead5	221	$qgradeavgsql = "SELECT qs.question, AVG(qs.grade) FROM " .
	222	"{question_sessions} qns, " .
	223	"{question_states} qs, " .
	224	"{question} q, " .
	225	$fromqa.' '.
	226	'WHERE ' .$whereqa.
	227	'AND qns.attemptid = qa.uniqueid '.
	228	'AND qs.question = q.id ' .
	229	'AND q.length > 0 '.
	230	$usingattempts->sql.
	231	'AND qns.newgraded = qs.id GROUP BY qs.question';
	232	$qgradeavgs = $DB->get_records_sql_menu($qgradeavgsql, array($quiz->id));
	233	$sum = 0;
040c36e3	234	$sql = 'SELECT ' .
	235	'SUM(POWER((qs.grade - ?),2)) AS power2 ' .
	236	'FROM ' .
	237	'{question_sessions} qns, ' .
	238	'{question_states} qs, ' .
	239	'{question} q, ' .
	240	$fromqa.' '.
	241	'WHERE ' .$whereqa.
	242	'AND qns.attemptid = qa.uniqueid '.
	243	'AND qs.question = ? ' .
	244	$usingattempts->sql.
	245	'AND qns.newgraded = qs.id';
08a7ead5	246	foreach ($qgradeavgs as $qid => $qgradeavg){
08a7ead5	247	$params = array($qgradeavg, $quiz->id, $qid);
	248	$power = $DB->get_field_sql($sql, $params);
	249	if ($power === false){
	250	print_error('errorpowerquestions', 'quiz_statistics');
	251	}
	252	$sum += $power;
	253	}
	254	$sumofvarianceforallpositions = $sum / ($usingattempts->countrecs -1);
	255	$p = count($qgradeavgs);//no of positions
	256	$cic = (100 * $p / ($p -1)) * (1 - ($sumofvarianceforallpositions/$k2));
	257	$quizattsstatistics->data[] = array(get_string('cic', 'quiz_statistics'), number_format($cic, $quiz->decimalpoints).' %');
	258	$errorratio = 100 * sqrt(1-($cic/100));
	259	$quizattsstatistics->data[] = array(get_string('errorratio', 'quiz_statistics'), number_format($errorratio, $quiz->decimalpoints).' %');
	260	$standarderror = ($errorratio * $sd / 100);
	261	$quizattsstatistics->data[] = array(get_string('standarderror', 'quiz_statistics'),
	262	quiz_report_scale_sumgrades_as_percentage($standarderror, $quiz));
0c1c764e	263	print_table($quizattsstatistics);
c0250840	264
	265	}
	266	if (!$table->is_downloading()){
	267	print_heading(get_string('quizstructureanalysis', 'quiz_statistics'));
	268	}
	269	$table->setup($quiz, $cm->id, $reporturl);
	270	foreach ($questions as $question){
	271	$table->add_data_keyed($table->format_row($question));
08a7ead5	272	}
c0250840	273	$table->finish_output();
0c1c764e	274	return true;
	275	}
	276
	277	}
	278
	279
	280	?>