Groups of 'individuals'

The' individuals' that are represented by crosses on a scatterplot can often be split into different groups according to other information about them. In Official Statistics, the 'individuals' usually correspond to countries or regions, and they can be split into similar groups in various ways.

In a scatterplot, the crosses can be drawn with different symbols or in different colours to represent the group membership.

This will be clearer in an example.

Birth rate and life expectancy

The scatterplot below again describes the relationship between the birth rate and life expectancy of all countries in the world in 2005. The colours distinguish between the countries with low, medium and high GDP (less than US$1,000 per capita in 2005, between US$1,000 and US$10,000, and over US$10,000).

The three groups of countries separate out reasonably well — the countries with high GDP tend to have high life expectancy and low birth rate. However there are a few exceptions (especially red circles in the top left). Click on them to identify the countries.

Select Urban/Rural from the pop-up menu. The different symbols and colours now distinguish between countries in which the majority of the population is urban or rural.

Finally select Regions from the pop-up menu to use the colours and symbols to distinguish between different regions of the world.

Extra information can be added to a scatterplot to help understand the relationship between the main two measurements.