Median
Topic: Geographical Data: Sources, Compilation and Processing · NCERT: Class 12, Ch 2 "Data Processing"; Class 12, Ch 4 "Spatial Information Technology"
Meaning
The median is a positional average. It is found by its place in the series, not by adding values. When the values are arranged in order, the median is the value that splits them into two equal halves. For ungrouped data it is the value of the (N+1)/2th item. For grouped data it is M = l + (i/f)(N/2 − c). Because it depends only on position, extreme values do not affect it.
Example
NCERT arranges the heights of seven Himalayan peaks, from 7,817 m to 8,848 m (Mount Everest, on the Nepal–China border). The (7+1)/2 = 4th peak gives the median, 8,172 m.
Don't confuse with
- Mean: adds all values, so one very high or very low value pulls it away from the centre.