Bar Graphs – GCSE Mathematics (Foundation) AQA Revision

Bar graphs are used to present and compare data in a visual, easy-to-understand format.
Each bar in a bar graph represents a category or group of data. The height or length of the bar indicates the value associated with that category.
The horizontal axis (or x-axis) usually represents the categories of data being measured.
The vertical axis (or y-axis) usually represents the values for each of the categories.
Bars can be drawn horizontally or vertically. Most commonly, bar graphs are drawn vertically.

Choose the scale for the x-axis and y-axis carefully, ensuring the data fits and is displayed accurately.
Label each axis with what it represents. Include units if the data comes with a particular measurement unit (e.g., time in hours, length in meters).
Decide the width of each bar. All bars should have the same width. The distance between each bar is usually the same.
Use different colours for different categories if necessary to make the graph easier to interpret.
Provide a key or legend if multiple sets of data are represented in the same graph.
Always give the graph a title that succinctly describes what the graph shows.

Examine the bars in the graph to understand the values they represent.
Analyse the height or length of bars to compare between categories or to understand trends.
Use the values represented by the bars to compare categories or make interpretations.

Bar graphs are crucial in probability and statistics for visualising data distributions.
For probability, bar graphs can display the frequency of outcomes.
In statistics, bar graphs often represent quantitative data grouped into reasonably sized categories.
Probabilities can be estimated from a bar graph by comparing the relative heights of the bars.

Mislabelling or not labelling the axes.
Choosing an inappropriate scale that distorts the data.
Misinterpreting the data due to overlooked details such as a broken y-axis or misread labels.
Drawing bar widths inconsistently.