The midpoint of the upper and lower limits of a group is called the group median, which is a simple average of the upper and lower limits of each group, that is, the group median = (upper limit+upper limit) /2. The median value in a group is often used to represent the average level of each group of marker values.

For example, if one group is [200,250], then the median value in the group =(200+250)/2=225.