public double p50() {
    return getLinearInterpolation(0.50);
  }
@Test
  public void testP50() {
    HistogramData histogramData1 = HistogramData.linear(0, 0.2, 50);
    histogramData1.record(0, 1, 2, 3, 4, 5, 6, 7, 8, 9);
    assertThat(String.format("%.3f", histogramData1.p50()), equalTo("4.200"));

    HistogramData histogramData2 = HistogramData.linear(0, 0.02, 50);
    histogramData2.record(0, 0, 0);
    assertThat(String.format("%.3f", histogramData2.p50()), equalTo("0.010"));
  }