Usually median for data with ties, tied values are treated as
exactly same. For example, median of {3, 3, 4, 4, 4} will be 4.
However, the measured values are usually rounded, so that we can
assume evenly distributed true values for tied values. For example,
the previous data can be treated as rounded values of {2.75, 3.25,
11/3, 4, 13/3}. From this viewpoint, true median of {3, 3, 4, 4, 4}
could be 11/3 (=3.66...). This function calculates this.