Cambridge O Level Mathematics (Syllabus D) · Syllabus 4024 · Statistics
Cumulative Frequency Diagrams
What is Cumulative Frequency Diagrams?
A diagram built from the running totals of a grouped frequency table. Each running total is plotted against the upper boundary of its class, the curve starts at the lower boundary of the first class with cumulative frequency zero, and the points are joined with a smooth increasing curve. Because the vertical axis counts how many observations fall at or below each value, the curve can be read in both directions: horizontally at N over 4, N over 2 and three N over 4 to estimate the lower quartile, median and upper quartile, at p over 100 of N for any percentile, and vertically from a data value to find how many observations lie below or above it. The interquartile range, Q3 minus Q1, measures the spread of the middle fifty per cent and is unaffected by extreme values.
This definition is part of the Statistics chapter in Cambridge O Level Mathematics (Syllabus D).