Defined as the middle value of a data set (or sample) when the values are arranged in order (by size ranking, in ascending or descending order). Note that for an odd number of values in an ordered data set, the median is identified as the value which divides the data set into two data sets of equal size on each side of the median or middle value. For an even number of values arranged in order, the median is found by simply calculating the value mid-way between the two middle values. Note that the position of the median value of an ordered data set containing n observations may be found by using the formula: position of the median = n/2 + 1/2.