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Median from ogive

The median from an ogive is found by using the total frequency, locating N/2 on the cumulative frequency axis, and reading the corresponding class boundary value.

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Student-friendly explanation

To get the median from an ogive, we first find N/2 on the y-axis. From that point, we move horizontally to the curve and then vertically down to the x-axis. The value read on the x-axis is the median estimate.

How to write this in exams

  1. 1

    Start with the exact idea

    The median from an ogive is found by using the total frequency, locating N/2 on the cumulative frequency axis, and reading the corresponding class boundary value.

  2. 2

    Then show how to use it

    1. Find total frequency N. 2. Compute N/2. 3. Mark N/2 on the cumulative frequency axis. 4. Move horizontally to the ogive. 5. Drop vertically to read the median on the x-axis.

  3. 3

    Add one concrete example

    If total frequency is 40, we locate 20 on the cumulative frequency axis and read the matching x-value from the ogive.

  4. 4

    Avoid this incomplete answer

    A common wrong answer is to read the median from the y-axis or to use the highest point of the curve.

Definition

The median from an ogive is found by using the total frequency, locating N/2 on the cumulative frequency axis, and reading the corresponding class boundary value.

Example

If total frequency is 40, we locate 20 on the cumulative frequency axis and read the matching x-value from the ogive.

Rule to remember

Median from ogive is read at the x-value corresponding to N/2 on the y-axis of the less-than curve.

Memory hook

Half the total on y-axis, then read across and down.

Examples and method

Worked example

If the total frequency is 50, then N/2 = 25. Mark 25 on the cumulative frequency axis, meet the ogive, and drop a perpendicular to the x-axis to read the median value.

Method to apply

1. Find total frequency N. 2. Compute N/2. 3. Mark N/2 on the cumulative frequency axis. 4. Move horizontally to the ogive. 5. Drop vertically to read the median on the x-axis.

Diagram support

Draw the ogive, mark N/2 on the y-axis, move horizontally to the curve, then vertically to the x-axis.

How CBSE asks it

Students may be given an ogive and asked to estimate the median directly from the graph.

Avoid common mistakes

Common confusion

Students sometimes read the median from the wrong axis or forget to use half of the total frequency.

Common wrong answer

A common wrong answer is to read the median from the y-axis or to use the highest point of the curve.

Exam tip

Use a ruler and mark the horizontal and vertical steps carefully; one small reading error changes the answer.

Quick check

Why do we use N/2 while finding the median from an ogive?

We use N/2 because the median divides the data into two equal parts. On the ogive, this middle position helps us locate the value that separates the lower half from the upper half.

Answer writing and exam use

1-mark answer

The median from an ogive is found by using the total frequency, locating N/2 on the cumulative frequency axis, and reading the corresponding class boundary value.

2-mark answer

The median from an ogive is found by using the total frequency, locating N/2 on the cumulative frequency axis, and reading the corresponding class boundary value. Median from ogive is read at the x-value corresponding to N/2 on the y-axis of the less-than curve. If total frequency is 40, we locate 20 on the cumulative frequency axis and read the matching x-value from the ogive.

3-mark answer

To get the median from an ogive, we first find N/2 on the y-axis. From that point, we move horizontally to the curve and then vertically down to the x-axis. The value read on the x-axis is the median estimate. Median from ogive is read at the x-value corresponding to N/2 on the y-axis of the less-than curve. If the total frequency is 50, then N/2 = 25. Mark 25 on the cumulative frequency axis, meet the ogive, and drop a perpendicular to the x-axis to read the median value. Students may be given an ogive and asked to estimate the median directly from the graph. A common wrong answer is to read the median from the y-axis or to use the highest point of the curve.
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