Correlation

A correlation shows a connection between a factor and an outcome.

To describe a correlation in words state:

  • the change in the factor
  • how the outcome changes as this happens
  • how the pattern of change in each factor is similar or different

Here is an example, with each marking point shown as [1]:

'As carbon dioxide levels increase [1], the global average temperature increases [1] and the increases follow a similar pattern [1].'

Correlations in tables

To spot correlations in data, look at how the numbers change in each column of the data table.

FactorOutcome
As the values of the data here increase……the values of the data here increase in a similar way.

The trend in the outcome is the same as the factor.

FactorOutcome
As the values of the data here increase……the values of the data here decrease in an opposite way.

The trend in the outcome is the opposite of the trend in the factor.

Data which does not show a correlation has no similar or opposite trend in the outcome.

FactorOutcome
As the values of the data here increase……the values of the data here go up, down or do not change.

The upwards trend is the factor not present in the outcome.

Correlations in graphs

Graphs can also reveal correlations.

This graph shows increasing carbon dioxide levels in the atmosphere.

Graph shows how carbon dioxide has increased between 1700 and 2000. In the year 1700 there was 0.028% CO2 in the atmosphere, but at around 1850 this began to rise. By 2000, the percentage of CO2 was at 0.035, an increase of 0.007%

This graph shows a similar increase in global average temperature.

Graph showing how the global average temperature has changed from around 1870 - 2000. The line graph shows an increase in global temperature

It is important that the graphs show similar trends. This is most easily seen if graphs are overlaid on top of each other.