loncom/interface/statistics/lonproblemstatistics.pm - view

File: [LON-CAPA] / loncom / interface / statistics / lonproblemstatistics.pm
Revision 1.63: download - view: text, annotated - select for diffs
Tue Dec 9 21:14:23 2003 UTC (20 years, 5 months ago) by matthew
Branches: MAIN
CVS tags: version_1_1_X, version_1_1_3, version_1_1_2, version_1_1_1, version_1_1_0, version_1_0_99_3, version_1_0_99_2, version_1_0_99_1, HEAD

Bug 2371 is fixed!

# The LearningOnline Network with CAPA # # $Id: lonproblemstatistics.pm,v 1.63 2003/12/09 21:14:23 matthew Exp $ # # Copyright Michigan State University Board of Trustees # # This file is part of the LearningOnline Network with CAPA (LON-CAPA). # # LON-CAPA is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation; either version 2 of the License, or # (at your option) any later version. # # LON-CAPA is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with LON-CAPA; if not, write to the Free Software # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA # # /home/httpd/html/adm/gpl.txt # # http://www.lon-capa.org/ # # (Navigate problems for statistical reports # ############################################### ############################################### =pod =head1 NAME lonproblemstatistics =head1 SYNOPSIS Routines to present problem statistics to instructors via tables, Excel files, and plots. =over 4 =cut ############################################### ############################################### package Apache::lonproblemstatistics; use strict; use Apache::lonnet(); use Apache::loncommon(); use Apache::lonhtmlcommon; use Apache::loncoursedata; use Apache::lonstatistics; use Apache::lonlocal; use Spreadsheet::WriteExcel; ## ## Localization notes: ## ## in @Fields[0]->{'long_title'} is placed in Excel files and is used as the ## header for plots created with Graph.pm, both of which more than likely do ## not support localization. ## my @Fields = ( { name => 'problem_num', title => 'P#', align => 'right', color => '#FFFFE6' }, { name => 'container', title => 'Sequence or Folder', align => 'left', color => '#FFFFE6', sortable => 'yes' }, { name => 'title', title => 'Title', align => 'left', color => '#FFFFE6', special => 'link', sortable => 'yes', }, { name => 'part', title => 'Part', align => 'left', color => '#FFFFE6', }, { name => 'num_students', title => '#Stdnts', align => 'right', color => '#EEFFCC', format => '%d', sortable => 'yes', graphable => 'yes', long_title => 'Number of Students Attempting Problem' }, { name => 'tries', title => 'Tries', align => 'right', color => '#EEFFCC', format => '%d', sortable => 'yes', graphable => 'yes', long_title => 'Total Number of Tries' }, { name => 'max_tries', title => 'Max Tries', align => 'right', color => '#DDFFFF', format => '%d', sortable => 'yes', graphable => 'yes', long_title => 'Maximum Number of Tries' }, { name => 'mean_tries', title => 'Mean Tries', align => 'right', color => '#DDFFFF', format => '%5.2f', sortable => 'yes', graphable => 'yes', long_title => 'Average Number of Tries' }, { name => 'std_tries', title => 'S.D. tries', align => 'right', color => '#DDFFFF', format => '%5.2f', sortable => 'yes', graphable => 'yes', long_title => 'Standard Deviation of Number of Tries' }, { name => 'skew_tries', title => 'Skew Tries', align => 'right', color => '#DDFFFF', format => '%5.2f', sortable => 'yes', graphable => 'yes', long_title => 'Skew of Number of Tries' }, { name => 'deg_of_diff', title => 'DoDiff', align => 'right', color => '#DDFFFF', format => '%5.2f', sortable => 'yes', graphable => 'yes', long_title => 'Degree of Difficulty'. '[ 1 - ((#YES+#yes) / Tries) ]'}, { name => 'num_solved', title => '#YES', align => 'right', color => '#FFDDDD', format => '%4.1f',# format => '%d', sortable => 'yes', graphable => 'yes', long_title => 'Number of Students able to Solve' }, { name => 'num_override', title => '#yes', align => 'right', color => '#FFDDDD', format => '%4.1f',# format => '%d', sortable => 'yes', graphable => 'yes', long_title => 'Number of Students given Override' }, { name => 'per_wrong', title => '%Wrng', align => 'right', color => '#FFFFE6', format => '%4.1f', sortable => 'yes', graphable => 'yes', long_title => 'Percent of students whose final answer is wrong' }, ); ############################################### ############################################### =pod =item &CreateInterface() Create the main intereface for the statistics page. Allows the user to select sections, maps, and output. =cut ############################################### ############################################### my @OutputOptions = ( { name => 'problem statistics grouped by sequence', value => 'HTML problem statistics grouped', description => 'Output statistics for the problem parts.', mode => 'html', show => 'grouped', }, { name => 'problem statistics ungrouped', value => 'HTML problem statistics ungrouped', description => 'Output statistics for the problem parts.', mode => 'html', show => 'ungrouped', }, { name => 'problem statistics, Excel', value => 'Excel problem statistics', description => 'Output statistics for the problem parts '. 'in an Excel workbook', mode => 'excel', show => 'all', }, ); sub CreateInterface { my $Str = ''; $Str .= '<table cellspacing="5">'."\n"; $Str .= '<tr>'; $Str .= '<td align="center"><b>'.&mt('Sections').'</b></td>'; $Str .= '<td align="center"><b>'.&mt('Enrollment Status').'</b></td>'; $Str .= '<td align="center"><b>'.&mt('Sequences and Folders').'</b></td>'; $Str .= '<td align="center"><b>'.&mt('Output').'</b></td>'; $Str .= '</tr>'."\n"; # $Str .= '<tr><td align="center">'."\n"; $Str .= &Apache::lonstatistics::SectionSelect('Section','multiple',5); $Str .= '</td><td align="center">'; $Str .= &Apache::lonhtmlcommon::StatusOptions(undef,undef,5); $Str .= '</td><td align="center">'; # my $only_seq_with_assessments = sub { my $s=shift; if ($s->{'num_assess'} < 1) { return 0; } else { return 1; } }; $Str .= &Apache::lonstatistics::MapSelect('Maps','multiple,all',5, $only_seq_with_assessments); $Str .= '</td><td>'."\n"; my ($html,$outputmode,$show) = &Apache::lonstatistics::CreateAndParseOutputSelector( 'statsoutputmode', 'HTML problem statistics grouped', @OutputOptions); $Str .= $html; $Str .= '</td></tr>'."\n"; $Str .= '</table>'."\n"; $Str .= '<input type="submit" name="GenerateStatistics" value="'. &mt('Generate Statistics').'" />'; $Str .= ' 'x5; $Str .= '<input type="submit" name="ClearCache" value="'. &mt('Clear Caches').'" />'; $Str .= ' 'x5; return ($Str,$outputmode,$show); } ############################################### ############################################### =pod =item &BuildProblemStatisticsPage() Main interface to problem statistics. =cut ############################################### ############################################### sub BuildProblemStatisticsPage { my ($r,$c)=@_; # my %Saveable_Parameters = ('Status' => 'scalar', 'statsoutputmode' => 'scalar', 'Section' => 'array', 'StudentData' => 'array', 'Maps' => 'array'); &Apache::loncommon::store_course_settings('statistics', \%Saveable_Parameters); &Apache::loncommon::restore_course_settings('statistics', \%Saveable_Parameters); # &Apache::lonstatistics::PrepareClasslist(); # my ($interface,$output_mode,$show) = &CreateInterface(); $r->print($interface); $r->print('<input type="hidden" name="statsfirstcall" value="no" />'); $r->print('<input type="hidden" name="sortby" value="'.$ENV{'form.sortby'}. '" />'); $r->print('<input type="hidden" name="plot" value="" />'); if (! exists($ENV{'form.statsfirstcall'})) { return; } # &Apache::lonstatistics::Gather_Student_Data($r); # # if ($output_mode eq 'html') { $r->print("<h2>". $ENV{'course.'.$ENV{'request.course.id'}.'.description'}. "</h2>\n"); $r->print("<h3>".localtime(time)."</h3>"); $r->rflush(); if ($show eq 'grouped') { &output_html_grouped_by_sequence($r); } elsif ($show eq 'ungrouped') { &output_html_ungrouped($r); } } elsif ($output_mode eq 'excel') { $r->print('<h2>'.&mt('Preparing Excel Spreadsheet').'</h2>'); &output_excel($r); } else { $r->print('<h1>'.&mt('Not implemented').'</h1>'); } return; } ############################################### ############################################### =pod =item &output_html_grouped_by_sequence() Presents the statistics data as an html table organized by the order the assessments appear in the course. =cut ############################################### ############################################### sub output_html_grouped_by_sequence { my ($r) = @_; my $problem_num = 0; #$r->print(&ProblemStatisticsLegend()); foreach my $sequence (&Apache::lonstatistics::Sequences_with_Assess()) { next if ($sequence->{'num_assess'}<1); $r->print("<h3>".$sequence->{'title'}."</h3>"); $r->print('<table border="0"><tr><td bgcolor="#777777">'."\n"); $r->print('<table border="0" cellpadding="3">'."\n"); $r->print('<tr bgcolor="#FFFFE6">'); my $Str = &statistics_table_header('no container no plots'); $r->print('<tr bgcolor="#FFFFE6">'.$Str."</tr>\n"); foreach my $resource (@{$sequence->{'contents'}}) { next if ($resource->{'type'} ne 'assessment'); foreach my $part (@{$resource->{'parts'}}) { $problem_num++; my $data = &get_statistics($sequence,$resource,$part, $problem_num); my $option = ''; $r->print('<tr>'.&statistics_html_table_data($data, 'no container'). "</tr>\n"); } } $r->print("</table>\n"); $r->print("</td></tr></table>\n"); $r->rflush(); } # return; } ############################################### ############################################### =pod =item &output_html_ungrouped() Presents the statistics data in a single html table which can be sorted by different columns. =cut ############################################### ############################################### sub output_html_ungrouped { my ($r,$option) = @_; # if (exists($ENV{'form.plot'}) && $ENV{'form.plot'} ne '') { &plot_statistics($r,$ENV{'form.plot'}); } # my $problem_num = 0; my $show_container = 0; my $show_part = 0; #$r->print(&ProblemStatisticsLegend()); my $sortby = undef; foreach my $field (@Fields) { if ($ENV{'form.sortby'} eq $field->{'name'}) { $sortby = $field->{'name'}; } } if (! defined($sortby) || $sortby eq '' || $sortby eq 'problem_num') { $sortby = 'container'; } # If there is more than one sequence, list their titles my @Sequences = &Apache::lonstatistics::Sequences_with_Assess(); if (@Sequences < 1) { $option .= ' no container'; } # # Compile the data my @Statsarray; foreach my $sequence (@Sequences) { next if ($sequence->{'num_assess'}<1); foreach my $resource (@{$sequence->{'contents'}}) { next if ($resource->{'type'} ne 'assessment'); foreach my $part (@{$resource->{'parts'}}) { $problem_num++; my $data = &get_statistics($sequence,$resource,$part, $problem_num); $show_part = 1 if ($part ne '0'); # push (@Statsarray,$data); } } } # # Sort the data my @OutputOrder; if ($sortby eq 'container') { @OutputOrder = @Statsarray; } else { # $sortby is already defined, so we can charge ahead if ($sortby =~ /^(title|part)$/i) { # Alpha comparison @OutputOrder = sort { lc($a->{$sortby}) cmp lc($b->{$sortby}) || lc($a->{'title'}) cmp lc($b->{'title'}) || lc($a->{'part'}) cmp lc($b->{'part'}); } @Statsarray; } else { # Numerical comparison @OutputOrder = sort { my $retvalue = 0; if ($b->{$sortby} eq 'nan') { if ($a->{$sortby} ne 'nan') { $retvalue = -1; } else { $retvalue = 0; } } if ($a->{$sortby} eq 'nan') { if ($b->{$sortby} ne 'nan') { $retvalue = 1; } } if ($retvalue eq '0') { $retvalue = $b->{$sortby} <=> $a->{$sortby} || lc($a->{'title'}) <=> lc($b->{'title'}) || lc($a->{'part'}) <=> lc($b->{'part'}); } $retvalue; } @Statsarray; } } $option .= 'no part' if (! $show_part); my $num_output = 0; # # output the headers $r->print('<table border="0"><tr><td bgcolor="#777777">'."\n"); $r->print('<table border="0" cellpadding="3">'."\n"); my $Str = &statistics_table_header($option.' sortable'); $r->print('<tr bgcolor="#FFFFE6">'.$Str."</tr>\n"); # foreach my $rowdata (@OutputOrder) { $num_output++; if ($num_output % 25 == 0) { $r->print("</table>\n</td></tr></table>\n"); # $r->print('<table border="0"><tr><td bgcolor="#777777">'."\n"); $r->print('<table border="0" cellpadding="3">'."\n"); my $Str = &statistics_table_header($option.' sortable'); $r->print('<tr bgcolor="#FFFFE6">'.$Str."</tr>\n"); $r->rflush(); } $r->print('<tr>'.&statistics_html_table_data($rowdata,$option). "</tr>\n"); } $r->print("</table>\n"); $r->print("</td></tr></table>\n"); $r->rflush(); # return; } ############################################### ############################################### =pod =item &output_excel() Presents the statistical data in an Excel 95 compatable spreadsheet file. =cut ############################################### ############################################### sub output_excel { my ($r) = @_; my $filename = '/prtspool/'. $ENV{'user.name'}.'_'.$ENV{'user.domain'}.'_'. time.'_'.rand(1000000000).'.xls'; # my $excel_workbook = undef; my $excel_sheet = undef; # my $rows_output = 0; my $cols_output = 0; # # Create sheet $excel_workbook = Spreadsheet::WriteExcel->new('/home/httpd'.$filename); # # Check for errors if (! defined($excel_workbook)) { $r->log_error("Error creating excel spreadsheet $filename: $!"); $r->print(&mt("Problems creating new Excel file. ". "This error has been logged. ". "Please alert your LON-CAPA administrator.")); return ; } # # The excel spreadsheet stores temporary data in files, then put them # together. If needed we should be able to disable this (memory only). # The temporary directory must be specified before calling 'addworksheet'. # File::Temp is used to determine the temporary directory. $excel_workbook->set_tempdir($Apache::lonnet::tmpdir); # # Add a worksheet my $sheetname = $ENV{'course.'.$ENV{'request.course.id'}.'.description'}; if (length($sheetname) > 31) { $sheetname = substr($sheetname,0,31); } $excel_sheet = $excel_workbook->addworksheet( &Apache::loncommon::clean_excel_name($sheetname) ); # # Put the course description in the header $excel_sheet->write($rows_output,$cols_output++, $ENV{'course.'.$ENV{'request.course.id'}.'.description'}); $cols_output += 3; # # Put a description of the sections listed my $sectionstring = ''; my @Sections = @Apache::lonstatistics::SelectedSections; if (scalar(@Sections) > 1) { if (scalar(@Sections) > 2) { my $last = pop(@Sections); $sectionstring = "Sections ".join(', ',@Sections).', and '.$last; } else { $sectionstring = "Sections ".join(' and ',@Sections); } } else { if ($Sections[0] eq 'all') { $sectionstring = "All sections"; } else { $sectionstring = "Section ".$Sections[0]; } } $excel_sheet->write($rows_output,$cols_output++,$sectionstring); $cols_output += scalar(@Sections); # # Put the date in there too $excel_sheet->write($rows_output,$cols_output++, 'Compiled on '.localtime(time)); # $rows_output++; $cols_output=0; # # Long Headersheaders foreach my $field (@Fields) { next if ($field->{'name'} eq 'problem_num'); if (exists($field->{'long_title'})) { $excel_sheet->write($rows_output,$cols_output++, $field->{'long_title'}); } else { $excel_sheet->write($rows_output,$cols_output++,''); } } $rows_output++; $cols_output=0; # Brief headers foreach my $field (@Fields) { next if ($field->{'name'} eq 'problem_num'); # Use english for excel as I am not sure how well excel handles # other character sets.... $excel_sheet->write($rows_output,$cols_output++,$field->{'title'}); } $rows_output++; # # Write the data my $problem_num=0; foreach my $sequence (&Apache::lonstatistics::Sequences_with_Assess()) { next if ($sequence->{'num_assess'}<1); foreach my $resource (@{$sequence->{'contents'}}) { next if ($resource->{'type'} ne 'assessment'); foreach my $part (@{$resource->{'parts'}}) { $cols_output=0; $problem_num++; my $data = &get_statistics($sequence,$resource,$part, $problem_num); # if (!defined($part) || $part eq '') { $part = ' '; } foreach my $field (@Fields) { next if ($field->{'name'} eq 'problem_num'); $excel_sheet->write($rows_output,$cols_output++, $data->{$field->{'name'}}); } $rows_output++; } } } # # Write the excel file $excel_workbook->close(); # Tell the user where to get their excel file $r->print('<br />'. '<a href="'.$filename.'">'. &mt('Your Excel Spreadsheet').'</a>'."\n"); $r->rflush(); return; } ############################################### ############################################### =pod =item &statistics_html_table_data() Help function used to format the rows for HTML table output. =cut ############################################### ############################################### sub statistics_html_table_data { my ($data,$options) = @_; my $row = ''; foreach my $field (@Fields) { next if ($options =~ /no $field->{'name'}/); $row .= '<td bgcolor="'.$field->{'color'}.'"'; if (exists($field->{'align'})) { $row .= ' align="'.$field->{'align'}.'"'; } $row .= '>'; if (exists($field->{'special'}) && $field->{'special'} eq 'link') { $row .= '<a href="'.$data->{$field->{'name'}.'.link'}.'">'; } if (exists($field->{'format'})) { $row .= sprintf($field->{'format'},$data->{$field->{'name'}}); } else { $row .= $data->{$field->{'name'}}; } if (exists($field->{'special'}) && $field->{'special'} eq 'link') { $row.= '</a>'; } $row .= '</td>'; } return $row; } sub statistics_table_header { my ($options) = @_; my $header_row; foreach my $field (@Fields) { next if ($options =~ /no $field->{'name'}/); $header_row .= '<th>'; if ($options =~ /sortable/ && exists($field->{'sortable'}) && $field->{'sortable'} eq 'yes') { $header_row .= '<a href="javascript:'. 'document.Statistics.sortby.value='."'".$field->{'name'}."'". ';document.Statistics.submit();">'; } $header_row .= &mt($field->{'title'}); if ($options =~ /sortable/) { $header_row.= '</a>'; } if ($options !~ /no plots/ && exists($field->{'graphable'}) && $field->{'graphable'} eq 'yes') { $header_row.=' ('; $header_row .= '<a href="javascript:'. "document.Statistics.plot.value='$field->{'name'}'". ';document.Statistics.submit();">'; $header_row .= &mt('plot').'</a>)'; } $header_row .= '</th>'; } return $header_row; } ############################################### ############################################### =pod =item &plot_statistics() =cut ############################################### ############################################### sub plot_statistics { my ($r,$datafield) = @_; my @Data; # # my $sortfield = undef; my $title = undef; foreach my $field (@Fields) { if ($datafield eq $field->{'name'} && exists($field->{'graphable'}) && $field->{'graphable'} eq 'yes') { $sortfield = $field->{'name'}; $title = $field->{'long_title'}; } } return if (! defined($sortfield) || $sortfield eq ''); # my $Max = 0; my $problem_num = 0; foreach my $sequence (&Apache::lonstatistics::Sequences_with_Assess()) { next if ($sequence->{'num_assess'}<1); foreach my $resource (@{$sequence->{'contents'}}) { next if ($resource->{'type'} ne 'assessment'); foreach my $part (@{$resource->{'parts'}}) { my $problem_number++; my $data = &get_statistics($sequence,$resource,$part, $problem_num); my $value = $data->{$sortfield}; $Max = $value if ($Max < $value); push (@Data,$value); } } } # # Print out plot request my $yaxis = ''; if ($sortfield eq 'per_wrong') { $yaxis = 'Percent'; } # # Determine appropriate value for $Max if ($sortfield eq 'deg_of_diff') { if ($Max > 0.5) { $Max = 1; } elsif ($Max > 0.2) { $Max = 0.5; } elsif ($Max > 0.1) { $Max = 0.2; } } elsif ($sortfield eq 'per_wrong') { if ($Max > 50) { $Max = 100; } elsif ($Max > 25) { $Max = 50; } elsif ($Max > 20) { $Max = 25; } elsif ($Max > 10) { $Max = 20; } elsif ($Max > 5) { $Max = 10; } else { $Max = 5; } } $r->print("<p>".&Apache::loncommon::DrawBarGraph($title, 'Problem Number', $yaxis, $Max, undef, \@Data)."</p>\n"); # # Print out the data $ENV{'form.sortby'} = 'Contents'; # &output_html_ungrouped($r); return; } sub get_statistics { my ($sequence,$resource,$part,$problem_num) = @_; # my $symb = $resource->{'symb'}; my $courseid = $ENV{'request.course.id'}; # my $students = \@Apache::lonstatistics::Students; if ($Apache::lonstatistics::SelectedSections[0] eq 'all') { $students = undef; } my $data = &Apache::loncoursedata::get_problem_statistics ($students,$symb,$part,$courseid); $data->{'part'} = $part; $data->{'problem_num'} = $problem_num; $data->{'container'} = $sequence->{'title'}; $data->{'title'} = $resource->{'title'}; $data->{'title.link'} = $resource->{'src'}.'?symb='. &Apache::lonnet::escape($resource->{'symb'}); # return $data; } ############################################### ############################################### =pod =item &ProblemStatisticsLegend() HELP This needs to be localized, or at least generated automatically. =cut ############################################### ############################################### sub ProblemStatisticsLegend { my $Ptr = ''; $Ptr = '<table border="0">'; $Ptr .= '<tr><td>'; $Ptr .= '<b>#Stdnts</b></td>'; $Ptr .= '<td>Total number of students attempted the problem.'; $Ptr .= '</td></tr><tr><td>'; $Ptr .= '<b>Tries</b></td>'; $Ptr .= '<td>Total number of tries for solving the problem.'; $Ptr .= '</td></tr><tr><td>'; $Ptr .= '<b>Max Tries</b></td>'; $Ptr .= '<td>Largest number of tries for solving the problem by a student.'; $Ptr .= '</td></tr><tr><td>'; $Ptr .= '<b>Mean</b></td>'; $Ptr .= '<td>Average number of tries. [ Tries / #Stdnts ]'; $Ptr .= '</td></tr><tr><td>'; $Ptr .= '<b>#YES</b></td>'; $Ptr .= '<td>Number of students solved the problem correctly.'; $Ptr .= '</td></tr><tr><td>'; $Ptr .= '<b>#yes</b></td>'; $Ptr .= '<td>Number of students solved the problem by override.'; $Ptr .= '</td></tr><tr><td>'; $Ptr .= '<b>%Wrong</b></td>'; $Ptr .= '<td>Percentage of students who tried to solve the problem '; $Ptr .= 'but is still incorrect. [ 100*((#Stdnts-(#YES+#yes))/#Stdnts) ]'; $Ptr .= '</td></tr><tr><td>'; $Ptr .= '<b>DoDiff</b></td>'; $Ptr .= '<td>Degree of Difficulty of the problem. '; $Ptr .= '[ 1 - ((#YES+#yes) / Tries) ]'; $Ptr .= '</td></tr><tr><td>'; $Ptr .= '<b>S.D.</b></td>'; $Ptr .= '<td>Standard Deviation of the tries. '; $Ptr .= '[ sqrt(sum((Xi - Mean)^2)) / (#Stdnts-1) '; $Ptr .= 'where Xi denotes every student\'s tries ]'; $Ptr .= '</td></tr><tr><td>'; $Ptr .= '<b>Skew.</b></td>'; $Ptr .= '<td>Skewness of the students tries.'; $Ptr .= '[(sqrt( sum((Xi - Mean)^3) / #Stdnts)) / (S.D.^3)]'; $Ptr .= '</td></tr><tr><td>'; $Ptr .= '<b>Dis.F.</b></td>'; $Ptr .= '<td>Discrimination Factor: A Standard for evaluating the '; $Ptr .= 'problem according to a Criterion<br>'; $Ptr .= '<b>[Criterion to group students into %27 Upper Students - '; $Ptr .= 'and %27 Lower Students]</b><br>'; $Ptr .= '<b>1st Criterion</b> for Sorting the Students: '; $Ptr .= '<b>Sum of Partial Credit Awarded / Total Number of Tries</b><br>'; $Ptr .= '<b>2nd Criterion</b> for Sorting the Students: '; $Ptr .= '<b>Total number of Correct Answers / Total Number of Tries</b>'; $Ptr .= '</td></tr>'; $Ptr .= '<tr><td><b>Disc.</b></td>'; $Ptr .= '<td>Number of Students had at least one discussion.'; $Ptr .= '</td></tr></table>'; return $Ptr; } #---- END Problem Statistics Web Page ---------------------------------------- 1; __END__