Cumulative Frequency and Ogives
Ages 16–18Difficulty adapts to you
Cumulative Frequency and Ogives
Cumulative frequency is a running total. For n observations, estimate Q1 at cumulative frequency n ÷ 4, the median at n ÷ 2, and Q3 at 3n ÷ 4. Plot cumulative frequency against the upper class boundary and read the required value from an ogive.
Your goals
- ✓You can build cumulative-frequency tables and estimate medians, quartiles, and percentiles from curves.
- ✓You can use Cumulative Frequency and Ogives, model correctly.
- ✓You can use the definitions, units, assumptions, and examples to check your answer.
Words to know
- Cumulative Frequency and Ogives:
- Build cumulative-frequency tables and estimate medians, quartiles, and percentiles from curves.
- model:
- A rule or representation used to describe a situation and make a prediction.
Examples
- 1For n = 80, the median is read at cumulative frequency 40, Q1 at 20, and Q3 at 60.
- 2The IQR is the horizontal difference between the Q3 and Q1 readings.
Check these
- • Do not skip the meaning of a term or give a result without explaining what it means.
- • Keep every number, symbol, label, and unit in its correct place.
- • Show enough working to check how you reached your answer.
Helpful habits
- • Read the whole question before choosing what to do.
- • Show one clear step at a time and check each step.
- • If you are stuck, draw a model, try smaller numbers, or revisit the example.
Now try your own
Create your own cumulative frequency and ogives example, solve it, and explain how you checked it.
Spark
Creativity & Innovation“Maths is like a puzzle — the fun is in figuring it out!”