Topic summary · IGCSE handout

Cumulative Frequency summary

Cumulative frequency graphs estimate medians and quartiles and lead to box plots and interquartile range.

Open Learning Sheet — Cumulative Frequency Download Cumulative Frequency answers PDF

Files: 32_cumulative_frequency_handout.pdf · 32_cumulative_frequency_handout_answers.pdf · free public downloads · diagrams in the PDFs

Key learning points

Plot upper-class boundaries against running totals; join with a smooth curve.
Median at total $/2$ ; Q1 at total $/4$ ; Q3 at $3\times$ total $/4$ .
IQR = Q3 − Q1 measures spread of the middle half.

Worked example 1 — Reading the median

CF graph, $n=80$ . CF height for the median?

Working

40

Read across from $n/2$ .

Worked example 2 — IQR

UQ $=12$ , LQ $=5$ . IQR?

Working

7

UQ − LQ.

Worked example 3 — Plotting

CF is plotted against which x-value?

Working

\text{upper class boundary}

Running total to the end of the class.

Scaffolded Learning Sheet and answers (PDFs)

This page is a short, searchable overview for revision and search engines. Use the Scaffolded Learning Sheet first, then the Answers PDF for a full written solution. The printable PDFs remain the main classroom resource.

Open Learning Sheet Answers PDF

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