# Stats - Cumulative Frequency

> Source: https://ollybritton.com/notes/a-level/maths/topics/stats/cumulative-frequency/ · Updated: 2020-11-12 · Tags: stats, maths

See also:
- [Stats - Median, Quartiles and Percentiles](https://ollybritton.com/notes/a-level/maths/topics/stats/median/)

##### What goes on the $x$-axis on a cumulative frequency diagram??
The variable being measured.

##### What does on the $y$-axis on a cumulative frequency diagram??
Cumulative frequency.

##### What is the purpose of a cumulative frequency diagram??
It allows you to find estimates for medians, quartiles and percentiles.

##### Drawing a cumulative frequency diagram is like what other process in stats??
Linear interpolation.

##### When plotting a cumulative frequency diagram for grouped data, which class boundary should you use for the point on the $x$-axis??
The lower class boundary.

##### I have a cumulative frequency diagram with a max frequency of 60. I want to find an estimate for the upper quartile. What should I do??
* $60 \div 4, \times 4 = 45$
* Find $45$ on the $y$-axis, draw a straight line to the curve.
* Draw a line from that point on the curve to the $x$-axis and that is the value.

##### How should you join the points on a cumulative frequency diagram??
With a smooth curve.

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