Drawing the charts papers ask for: line charts, time series, pie charts, frequency polygons, histograms, cumulative frequency graphs, box plots and lines of best fit.
What you will learn
- Draw a vertical line chart, a time series and a frequency polygon
- Work out pie chart angles
- Draw a histogram from frequency densities (Higher)
- Draw a cumulative frequency graph and read the median (Higher)
- Find the five values for a box plot (Higher)
- Draw a line of best fit and use it
Points in the right place
The frequency of a value is how many times it occurs.
Grouped data is sorted into classes such as 10 < h ≤ 20 (more than 10, up to and including 20); the class width is 20 − 10 = 10 and the midpoint is (10 + 20) ÷ 2 = 15.
Each chart has its own rule for where a point goes.
- Vertical line chart (discrete data): a line at each value, as tall as its frequency.
- Time series: one point for each time, joined with straight lines. Look for a pattern that repeats each year, and for the overall trend.
- Frequency polygon: each frequency plotted at the midpoint of its class, joined with straight lines.
- Cumulative frequency: the running total of the frequencies (frequencies 4, 9, 6 give 4, 13, 19). Plot each running total at the upper end of its class, start from the lower end of the first class at 0, and join with a smooth curve.
A time series for each quarter of two years usually rises and falls in the same pattern each year (with the seasons). To compare the years, add up each year's values. To compare one quarter with the same quarter a year later, use the percentage change: change ÷ original × 100.
The rest of this lesson and its 11 practice questions are locked.
In this lesson
- Points in the right place
- The mean from a table
- Pie charts and histograms
- Lines of best fit and box plots
11 practice questions, marked as you go; about 25 minutes in all.
Key terms
Frequency, Classes, Class width, Midpoint, Vertical line chart, Upper end, Mean, Estimate, Area, Scatter graph
In this unit: Drawing and constructing
The answers papers ask you to draw: graphs plotted from a table, sketches with their key points, statistical charts, ruler-and-compass constructions and loci, each checked the way a mark scheme checks it.