Four classes have frequencies 3, 7, 12 and 8. Write the cumulative frequencies.
Keep a running total.
Worked solution
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GCSE & IGCSE maths practice
Cumulative frequency is a running total of the frequencies. On a cumulative frequency graph, plot each running total at the upper bound of its class and join the points with a smooth curve. To estimate the median, read across from half the total; the quartiles are at a quarter and three quarters.
8 questions · Higher tier · Every answer is checked as you type it, with a full worked solution. Updated .
| GCSE (AQA, Edexcel, OCR) | Higher only: construct and interpret cumulative frequency graphs, including quartiles and the interquartile range. |
|---|---|
| Cambridge IGCSE (0580) | Extended only: draw and interpret cumulative frequency tables and diagrams, and estimate the median, percentiles, quartiles and interquartile range. |
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Four classes have frequencies 3, 7, 12 and 8. Write the cumulative frequencies.
Keep a running total.
Worked solution
A cumulative frequency graph shows 80 people. At what cumulative frequency do you read off the median?
Half the total.
Worked solution
For the same 80 people, at what cumulative frequency do you read off the lower quartile?
A quarter of the total.
Worked solution
From a cumulative frequency graph, the lower quartile is 23 and the upper quartile is 41. Find the interquartile range.
UQ − LQ.
Worked solution
How many people took between 20 and 30 minutes?
| Time, t (minutes) | Cumulative frequency |
|---|---|
| t ≤ 10 | 6 |
| t ≤ 20 | 20 |
| t ≤ 30 | 41 |
| t ≤ 40 | 50 |
Subtract the running totals.
Worked solution
Using the same table, how many people took more than 30 minutes?
| Time, t (minutes) | Cumulative frequency |
|---|---|
| t ≤ 10 | 6 |
| t ≤ 20 | 20 |
| t ≤ 30 | 41 |
| t ≤ 40 | 50 |
Total minus those up to 30.
Worked solution
Using the same table, what percentage of people took 20 minutes or less?
| Time, t (minutes) | Cumulative frequency |
|---|---|
| t ≤ 10 | 6 |
| t ≤ 20 | 20 |
| t ≤ 30 | 41 |
| t ≤ 40 | 50 |
20 out of 50.
Worked solution
The class has cumulative frequency 20. Which point do you plot?
Cumulative frequency goes at the upper bound.
Worked solution
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