A Level

# Maths skills

## 1. Graphs

Your findings can be presented with a range of graphical and mapping techniques. You should be able to justify each one.

### Bar chart

• Nominal data.
• Categories on x-axis.
• Bar height represents frequency.
• Leave gaps between bars as data are discontinuous.

There are many variations on the basic bar chart, such as divided bar chart, percentage bar chart and bi-polar analysis bar chart.

### Histogram

• Interval or ratio data.
• Bar area shows frequency.
• Bars are not necessarily of equal width.
• No gaps between bars as data are continuous. Example of a histogram. Size of clasts in two glacial deposits.

### Pie chart

• Nominal or ordinal data.
• Area of circle segment represents proportion.
• Multiple pie charts can be used with the radius of the circle having meaning.

### Line graph

• Ordinal, interval or ratio data.
• Both axes are numerical.
• If time is one of the variables, always plot it on the x-axis.
• Only join up the points if the data are continuous.