print "Test random number generator\n";
$s = 0;
$ss = 0;
$n = 100;
for ($i = 0; $i < $n; $i += 1) {
        $r = 2*rand();
        $s += $r;
        $ss += $r * $r;
}
$mean = $s / $n;
$stddev = sqrt($ss / $n - $mean*$mean);
$width = 1.96 * $stddev / sqrt($n);
print "Mean = $mean stddev = $stddev\n";
print "95% CI = ", $mean-$width," to ",$mean+$width,"\n";