## 1. Introduction, and choosing a graph or chart

Graphs and charts provide a powerful way of summarising data and presenting them in a way that most people find easy to read. They are an important alternative to tables, especially where a dataset is large, but remember that a graphical presentation of data is unlikely to allow your reader to access the raw data if they wish, whilst this is possible with a table. Graphs and charts may alo be useful in assessing data prior to udretaking data analysis or to fitting a numerical model.

The choice of an appropriate graph or chart depends on what information you are trying to convey. The three choices at the end of this introduction link to the next three sections. Finally there is a brief section on plotting graphs and charts using spreadsheets. Remember that each of the NuMBerS statistical toolkits includes guidance on the appropriate graphical presentation.

What is your graph going to do?

- Summarise the data - go to Section 2
- Illustrate the average and variability for a single set of observations, or the differences between more than one set of observations - go to Section 3
- Illustrate relationships between variables - go to Section 4