/**
* Compute the quiz statistics.
*
* @param int $quizid the quiz id.
* @param int $whichattempts which attempts to use, represented internally as one of the constants as used in
* $quiz->grademethod ie.
* QUIZ_GRADEAVERAGE, QUIZ_GRADEHIGHEST, QUIZ_ATTEMPTLAST or QUIZ_ATTEMPTFIRST
* we calculate stats based on which attempts would affect the grade for each student.
* @param array $groupstudents students in this group.
* @param int $p number of positions (slots).
* @param float $sumofmarkvariance sum of mark variance, calculated as part of question statistics
* @return quiz_statistics_calculated $quizstats The statistics for overall attempt scores.
*/
public function calculate($quizid, $whichattempts, $groupstudents, $p, $sumofmarkvariance)
{
$quizstats = new quiz_statistics_calculated($whichattempts);
$countsandaverages = $this->attempt_counts_and_averages($quizid, $groupstudents);
foreach ($countsandaverages as $propertyname => $value) {
$quizstats->{$propertyname} = $value;
}
$s = $quizstats->s();
if ($s == 0) {
return $quizstats;
}
// Recalculate sql again this time possibly including test for first attempt.
list($fromqa, $whereqa, $qaparams) = quiz_statistics_attempts_sql($quizid, $groupstudents, $whichattempts);
$quizstats->median = $this->median($s, $fromqa, $whereqa, $qaparams);
if ($s > 1) {
$powers = $this->sum_of_powers_of_difference_to_mean($quizstats->avg(), $fromqa, $whereqa, $qaparams);
$quizstats->standarddeviation = sqrt($powers->power2 / ($s - 1));
// Skewness.
if ($s > 2) {
// See http://docs.moodle.org/dev/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) * ($s - 2));
if ($k2 != 0) {
$quizstats->skewness = $k3 / pow($k2, 3 / 2);
// Kurtosis.
if ($s > 3) {
$k4 = $s * $s * (($s + 1) * $m4 - 3 * ($s - 1) * $m2 * $m2) / (($s - 1) * ($s - 2) * ($s - 3));
$quizstats->kurtosis = $k4 / ($k2 * $k2);
}
if ($p > 1) {
$quizstats->cic = 100 * $p / ($p - 1) * (1 - $sumofmarkvariance / $k2);
$quizstats->errorratio = 100 * sqrt(1 - $quizstats->cic / 100);
$quizstats->standarderror = $quizstats->errorratio * $quizstats->standarddeviation / 100;
}
}
}
}
$quizstats->cache(quiz_statistics_qubaids_condition($quizid, $groupstudents, $whichattempts));
return $quizstats;
}
/**
* Display the report.
*/
public function display($quiz, $cm, $course)
{
global $CFG, $DB, $OUTPUT, $PAGE;
$this->context = context_module::instance($cm->id);
if (!quiz_questions_in_quiz($quiz->questions)) {
$this->print_header_and_tabs($cm, $course, $quiz, 'statistics');
echo quiz_no_questions_message($quiz, $cm, $this->context);
return true;
}
// Work out the display options.
$download = optional_param('download', '', PARAM_ALPHA);
$everything = optional_param('everything', 0, PARAM_BOOL);
$recalculate = optional_param('recalculate', 0, PARAM_BOOL);
// A qid paramter indicates we should display the detailed analysis of a sub question.
$qid = optional_param('qid', 0, PARAM_INT);
$slot = optional_param('slot', 0, PARAM_INT);
$whichattempts = optional_param('whichattempts', $quiz->grademethod, PARAM_INT);
$pageoptions = array();
$pageoptions['id'] = $cm->id;
$pageoptions['mode'] = 'statistics';
$reporturl = new moodle_url('/mod/quiz/report.php', $pageoptions);
$mform = new quiz_statistics_settings_form($reporturl);
$mform->set_data(array('whichattempts' => $whichattempts));
if ($fromform = $mform->get_data()) {
$whichattempts = $fromform->whichattempts;
}
if ($whichattempts != $quiz->grademethod) {
$reporturl->param('whichattempts', $whichattempts);
}
// Find out current groups mode.
$currentgroup = $this->get_current_group($cm, $course, $this->context);
$nostudentsingroup = false;
// True if a group is selected and there is no one in it.
if (empty($currentgroup)) {
$currentgroup = 0;
$groupstudents = array();
} else {
if ($currentgroup == self::NO_GROUPS_ALLOWED) {
$groupstudents = array();
$nostudentsingroup = true;
} else {
// All users who can attempt quizzes and who are in the currently selected group.
$groupstudents = get_users_by_capability($this->context, array('mod/quiz:reviewmyattempts', 'mod/quiz:attempt'), '', '', '', '', $currentgroup, '', false);
if (!$groupstudents) {
$nostudentsingroup = true;
}
}
}
$qubaids = quiz_statistics_qubaids_condition($quiz->id, $groupstudents, $whichattempts);
// If recalculate was requested, handle that.
if ($recalculate && confirm_sesskey()) {
$this->clear_cached_data($qubaids);
redirect($reporturl);
}
// Set up the main table.
$this->table = new quiz_statistics_table();
if ($everything) {
$report = get_string('completestatsfilename', 'quiz_statistics');
} else {
$report = get_string('questionstatsfilename', 'quiz_statistics');
}
$courseshortname = format_string($course->shortname, true, array('context' => context_course::instance($course->id)));
$filename = quiz_report_download_filename($report, $courseshortname, $quiz->name);
$this->table->is_downloading($download, $filename, get_string('quizstructureanalysis', 'quiz_statistics'));
$questions = $this->load_and_initialise_questions_for_calculations($quiz);
if (!$nostudentsingroup) {
// Get the data to be displayed.
list($quizstats, $questionstats, $subquestionstats) = $this->get_quiz_and_questions_stats($quiz, $whichattempts, $groupstudents, $questions);
} else {
// Or create empty stats containers.
$quizstats = new quiz_statistics_calculated($whichattempts);
$questionstats = array();
$subquestionstats = array();
}
// Set up the table, if there is data.
if ($quizstats->s()) {
$this->table->statistics_setup($quiz, $cm->id, $reporturl, $quizstats->s());
}
// Print the page header stuff (if not downloading.
if (!$this->table->is_downloading()) {
$this->print_header_and_tabs($cm, $course, $quiz, 'statistics');
if (groups_get_activity_groupmode($cm)) {
groups_print_activity_menu($cm, $reporturl->out());
if ($currentgroup && !$groupstudents) {
$OUTPUT->notification(get_string('nostudentsingroup', 'quiz_statistics'));
}
}
if (!$this->table->is_downloading() && $quizstats->s() == 0) {
echo $OUTPUT->notification(get_string('noattempts', 'quiz'));
}
// Print display options form.
$mform->display();
}
if ($everything) {
// Implies is downloading.
// Overall report, then the analysis of each question.
$quizinfo = $quizstats->get_formatted_quiz_info_data($course, $cm, $quiz);
$this->download_quiz_info_table($quizinfo);
if ($quizstats->s()) {
$this->output_quiz_structure_analysis_table($quizstats->s(), $questionstats, $subquestionstats);
if ($this->table->is_downloading() == 'xhtml' && $quizstats->s() != 0) {
$this->output_statistics_graph($quiz->id, $currentgroup, $whichattempts);
}
foreach ($questions as $slot => $question) {
if (question_bank::get_qtype($question->qtype, false)->can_analyse_responses()) {
$this->output_individual_question_response_analysis($question, $questionstats[$slot]->s, $reporturl, $qubaids);
} else {
if (!empty($questionstats[$slot]->subquestions)) {
$subitemstodisplay = explode(',', $questionstats[$slot]->subquestions);
foreach ($subitemstodisplay as $subitemid) {
$this->output_individual_question_response_analysis($subquestionstats[$subitemid]->question, $subquestionstats[$subitemid]->s, $reporturl, $qubaids);
}
}
}
}
}
$this->table->export_class_instance()->finish_document();
} else {
if ($slot) {
// Report on an individual question indexed by position.
if (!isset($questions[$slot])) {
print_error('questiondoesnotexist', 'question');
}
$this->output_individual_question_data($quiz, $questionstats[$slot]);
$this->output_individual_question_response_analysis($questions[$slot], $questionstats[$slot]->s, $reporturl, $qubaids);
// Back to overview link.
echo $OUTPUT->box('<a href="' . $reporturl->out() . '">' . get_string('backtoquizreport', 'quiz_statistics') . '</a>', 'backtomainstats boxaligncenter generalbox boxwidthnormal mdl-align');
} else {
if ($qid) {
// Report on an individual sub-question indexed questionid.
if (!isset($subquestionstats[$qid])) {
print_error('questiondoesnotexist', 'question');
}
$this->output_individual_question_data($quiz, $subquestionstats[$qid]);
$this->output_individual_question_response_analysis($subquestionstats[$qid]->question, $subquestionstats[$qid]->s, $reporturl, $qubaids);
// Back to overview link.
echo $OUTPUT->box('<a href="' . $reporturl->out() . '">' . get_string('backtoquizreport', 'quiz_statistics') . '</a>', 'boxaligncenter generalbox boxwidthnormal mdl-align');
} else {
if ($this->table->is_downloading()) {
// Downloading overview report.
$quizinfo = $quizstats->get_formatted_quiz_info_data($course, $cm, $quiz);
$this->download_quiz_info_table($quizinfo);
$this->output_quiz_structure_analysis_table($quizstats->s(), $questionstats, $subquestionstats);
$this->table->finish_output();
} else {
// On-screen display of overview report.
echo $OUTPUT->heading(get_string('quizinformation', 'quiz_statistics'), 3);
echo $this->output_caching_info($quizstats, $quiz->id, $groupstudents, $whichattempts, $reporturl);
echo $this->everything_download_options();
$quizinfo = $quizstats->get_formatted_quiz_info_data($course, $cm, $quiz);
echo $this->output_quiz_info_table($quizinfo);
if ($quizstats->s()) {
echo $OUTPUT->heading(get_string('quizstructureanalysis', 'quiz_statistics'), 3);
$this->output_quiz_structure_analysis_table($quizstats->s(), $questionstats, $subquestionstats);
$this->output_statistics_graph($quiz->id, $currentgroup, $whichattempts);
}
}
}
}
}
return true;
}