func generate_statistics(n) {
    var(sum=0, sum2=0);
    var hist = 10.of(0);

    n.times {
        var r = 1.rand;
        sum += r;
        sum2 += r**2;
        hist[10*r] += 1;
    }

    var mean = sum/n;
    var stddev = Math.sqrt(sum2/n - mean**2);

    say "size: #{n}";
    say "mean:   #{mean}";
    say "stddev: #{stddev}";

    var max = hist.max;
    hist.range.each {|i|
        printf("%.1f:%s\n", 0.1*i, "=" * 70*hist[i]/max);
    }
    print "\n";
}

[100, 1000, 10000].each {|n| generate_statistics(n) }