The Median – A Complete Simple Explanation

What is the Median?

The median is the middle value of a data set when the values are arranged in ascending (or descending) order. It divides the data into two equal halves — 50% of the values lie below it and 50% lie above it.

Unlike the mean, the median is not affected by extreme values (outliers). That is why we often use the median income of a village or the median marks of a class — it gives a more honest middle picture.

1) Median of Raw (Ungrouped) Data

Step 1 — Arrange in ascending order

Step 2 — Apply the formula based on n

2) Median of a Discrete Frequency Distribution

When data is given as values (x) with their frequencies (f), follow these steps:

  1. Arrange x in ascending order.
  2. Find the cumulative frequency (cf).
  3. Find N = Σf, then compute N/2.
  4. The value of x for which cf is just greater than or equal to N/2 is the median.

3) Median of a Continuous (Grouped) Frequency Distribution

For class intervals, first locate the median class — the class whose cumulative frequency first reaches or crosses N/2. Then apply:

Where:

  • L = lower limit of the median class
  • N = Σf (total frequency)
  • cf = cumulative frequency of the class before the median class
  • f = frequency of the median class
  • h = class width (size of the class interval)

Properties & When to Use Median

  • It is a positional average — depends on order, not actual values.
  • Not affected by extreme values — best for income, wages, land holdings, prices.
  • Can be calculated for open-end class intervals too.
  • Can be located graphically using ogives.
  • Sum of absolute deviations Σ|x − Median| is the least.

Practice Sums – Score Full Marks

Try each problem on paper first, then click Show step-by-step solution. Every step is written the way an Indian board / university examiner expects formula, substitution, simplification, and final answer with units (₹, kg, marks).

Tips to Score Full Marks

  • Always arrange data in ascending order for raw data — many students lose marks by skipping this step.
  • Write the formula first, then substitute. Examiners give step marks even if the final answer is wrong.
  • For grouped data, clearly state the median class with reason (“first cf ≥ N/2”).
  • Use the correct cf of the previous class in the formula — not the cf of the median class itself.
  • Always include units (₹, marks, kg, cm, years) in the final answer.
  • Round only at the final step, usually to 2 decimal places.

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