Definition
Arithmetic median is the middle value in a finite number of values arranged in ascending or descending order. Median is calculated by arranging data in ascending or descending order and then finding out the middle value. If data is even, then the sum of two middle values is divided by 2.

Formula
Median = n/2 if the data is odd, otherwise (n+1)/2

MS Excel
In MS Excel, median is calculated using "=Median(Range)" function. For example in the below demonstration a dataset of 2,4,6,8,10,12,14 has been defined in range A2:A8. In cell A9, we entered function "=Median(A2:A8)" and the result is '8' which is the arithmatic median of all those values.
For better understanding you can draw a chart. Create another column named Median right next to data column and enter '8' in front of each value. Now select both columns including their headings and press line chart in Insert>Charts tab.

Python
In python you can use "statistics" liberary to perform arithmetic median.
If you do not have python already installed, please download one with spider. Simplest ones are portable ones which do not need to be installed like winpython. You can download portable python from https://portablepython.com/
1. To import statistics type "import statistics as st"
2. You will also need pyplot liberary to draw a chart. Import pyplot using "import matplotlib.pyplot as pp"
3. Now define your data set as variable x using "x = [2,4,6,8,10,12,14]"
4. Now calculate median and store its value in variable "m", using "m = st.median(x)"
5. You can display the value of median computed above using print command. Type "print("Median: " + str(m))"
6. You can plot dataset on a line chart using "pp.plot(x,x)"
7. You can highlight the value of mean using "pp.plot(m,m,'o')"
8. In Spider, press Run and see the results. 