@staticmethod
def _quantile(data, percentile):
    """Find the percentile of a list of values.

        Args:
            data: A list of values.  N must be sorted.
            percentile: A float value from 0.0 to 1.0.
        Returns:
            The percentile of the values.
        """
    if len(data):
        n = int(round(percentile * len(data)))
        return data[n - 1]
