Determination of which statistical parameter requires quantities to be arranged in an ascending or descending order's -
The median 

A median is described as the value separating the higher half of a data set from the lower half.
It does not depend on the total, and number of items.
To obtain the median, the data is first arranged in an ascending or descending order of magnitude, and then the value of the middle observation is located, which is called median.
For example, diastolic BP of 9 individuals was as follows -

83, 75, 81, 79, 71, 95, 75, 77, 84
Now data is arranged in ascending order -
71, 75, 75, 77, 79, 81, 83, 84, 95

Here, 79 is the middle observation that is separating the upper four values from lower four values, so it is the median.
If there are two values in the middle instead of one, the median is worked out by taking the average of the two middle values.
For example, If diastolic BP of 10 individuals is as follows :-

83, 75, 81, 79, 71, 95, 75, 77, 84, 90
Data is arranged in ascending order -
71, 75, 75, 77, 79, 81, 83, 84, 90, 95


Here two values are separating the upper half of values from lower half. So the median here is -

Median = (79 + 81) / 2 = 80
Advantage of median

The value of median is not affected by abnormal very high or very low value.
Taking the example as was taken in mean -
The income of 7 people per day in rupees is as follows
5, 5, 5, 7,10, 20, 300 = (Total 352)
Here mean = 50.3
median = 7
The value of mean has affected seriously, whereas median is not affected, and median is more nearer to the truth.
So, median is used when the distribution of values is skewed (deviated) with some small number of very high values → median is used for skewed distribution.
Mean
Median
Mode
S.D