swk82

    rand('seed',123);

    outer_rounds = 100;
    inner_rounds = 100;
    items = 500;

    q99_mean_vec = [];
    q99_complete_vec = [];

    for ior = 1:outer_rounds;

      q99_vec = [];

      x = rand( 1, rounds*items );

      for iir = 1:inner_rounds
	
	q99_vec(iir) = quantile( x( (iir-1)*items+(1:items) )', 0.99 );
	
      end

      q99_complete_vec(ior) = quantile( x', 0.99 );
      q99_mean_vec(ior) = mean( q99_vec' );

    end

    hist( [ q99_complete_vec; q99_mean_vec ]', [0.988:0.0001:0.991] );
    xlim( [0.988, 0.991] );
    legend( 'from complete data', 'from means' );

  x <- runif(100000)
    quantile(x, 0.99)
    mean(sapply(1:2000, function(i) {
      i <- i * 50
      quantile(x[i-49:i], 0.99)
    }))