#!/usr/bin/perl

$sf = '[^\:]*\:';

@graderanges = ();

$total = 0;
$items = 0;

$sumsq = 0;

while (<>) {
  if (not /$sf$sf$sf$sf$sf$sf$sf$sf$sf$sf$sf$sf$sf$sf$sf$sf$sf$sf$sf$sf([^\:]*)\:[^\:]*$/) {
	print "FUCK! $_\n";
  }
  else {
 	$graderanges[$1 / 10]++;
	$total += $1;
	$sumsq += ($1 * $1);
	$items++;
  }
}

for (my $i = 0; $i <= 10; $i++) {
  print "$i" . "0-$i" . "9 : $graderanges[$i]\n";
}

$mean = $total / $items;
$var = ($sumsq - 2*$mean*$total + $items*$mean*$mean) / $items;
$stdev = sqrt($var);

print "Mean: $mean\nStd dev: $stdev\n";