# Binomial standard deviation, from PerlMonks node [477227]
# Standard deviation = SQR{(N*p*(1-p)} 
# Represent upvotes as 1, downvotes as 0 (or vice-versa)
sub b_stddev {
  my $N = @_ or return 0;
  my $p = (grep $_, @_) / $N;
  sqrt($N * $p * (1-$p));
}

my @samples = (1, 3, 8, 20);

for (map {my $x=$_; map [$x, $_], grep $x >= $_, @samples} @samples) {
  printf "%2d %2d: %3.4f\n", @$_, b_stddev((1) x $_->[0], (0) x $_->[1]);
}