Charts

Exam code: 2217

Written by: Ashika|Reviewed by: Caroline Carroll|Updated 2 July 2026

Bar Chart

A bar chart is the simplest form of displaying data
Each bar is the same width but can have varying lengths
Each bar is drawn an equal distance apart (equidistant)
The data is discrete data
Bar graphs are useful for:
- Comparing classes or groups of data
- Changes over time

Strengths	Summarises a large set of data Easy to interpret and construct Shows trends clearly
Limitations	Requires additional information Does not show causes, effects or patterns; can be too simplistic Can only be used with discrete data

Strengths	A large amount of data can be shown on one graph. Percentages and frequencies can be displayed on divided bar charts
Limitations	A divided bar chart can be difficult to read if there are multiple segments It can be difficult to compare data sometimes

The characteristics of a population—the distribution of age, sex, ethnicity, religion, etc.—are known as the population structure
The two main components of age and sex can be shown on a population pyramid
This is a graphical illustration of the distribution of a given population, grouped by age and gender
It can be used to represent a population of any region, city, country or even the world
As the population grows the shape of the pyramid changes
The population pyramid can be used to identify the following groups:
- Young dependants
- Old dependents
- Economically active (working population)
- Dependency ratio

Strengths	Easy to compare age and sex data Easy to read and annotate
Limitations	Can take a long time to construct Detail can be lost in the data (figures just show age groups there can be variation within the groups); additional annotations may be necessary

Used to show proportions, the area of the circle segment represents the proportion
A pie chart can also be drawn as a proportional circle
Pie charts can be located on maps to show variations at different sample sites
The percentage of the pie chart must add up to 100%
To calculate degrees of the pie chart (which totals 360°), divide the percentage by 100 and then multiply by 360
Each segment should be a different colour

Strengths	Clearly shows the proportion of the whole Easy to compare different components Easy to label Information can be highlighted by separating segments
Limitations	Does not show changes over time; hard to compare two sets of data Difficult to understand without clear labelling Calculating the size of each section can be difficult Can only be used for a small number of categories; otherwise, lots of segments become confusing

A rose diagram is a type of radial graph

Strengths	Clearly show patterns Multiple sets of data can be compared
Limitations	Can be difficult to plot Can only be used for certain types of data Hard to identify anomalies

Histograms show continuous data
Always use a ruler to draw the bars
All bars should be the same width
The top of the bar should reach the number on the side of the graph that is being represented
There should be no gaps; all bars should be touching
Ensure all axes are labelled and that the graph has a title

Strengths	Large data sets can be graphed easily Data can be compared
Limitations	Can be difficult to pinpoint exact data values They can only be used for numerical data