# Introduction

Graphs are one of the clearest ways to convey information about a single variable to an audience, particularly an audience that is unfamiliar or uncomfortable with numbers. While many people will claim that they do not understand statistics, they can look at a pie chart and get some sense of what a variable looks like. This is why we so frequently see graphs in newspapers and on television; they are an easy and effective way to convey information. It is important, however, to think carefully about how you construct graphs. In particular, you must consider which kind of graph will best convey the information you are interested in.

# Looking at a single variable: pie charts v. histograms

Pie charts and histograms are two of the most commonly used types of graphs used to convey information about a single variable; for this reason, they are called univariate graphs. Pie charts are the type we see most commonly, and one that many people are familiar with. However, each type offers different advantages in terms of how the information is presented. You should think carefully about these advantages before deciding which type to use.

## Pie charts

Pie charts are quite common, and you have probably run across them in news reports of various kinds. A pie chart looks at a single variable. That variable is divided into categories, and the proportion of the total cases in each category is calculated. A pie chart is simply a circle, divided into sections that reflect the proportions of each category.

### 2010 British Parliamentary Elections: a pie chart

The first example we'll look at is the wikipedia:United_Kingdom_general_election,_2010.

# References

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