Relationships

It is important to be able to identify relationships in data. This allows trends to be recognised and may allow for predictions to be made. Relationships in data can be identified in several ways.

Scatter graphs

Scatter graphs show the relationship between two sets of data, eg number of tourists and number of tourist facilities or weight and height.

Scatter graph recordiing height and weight of individuals

A line of best fit, or trend line, can be added to the scatter graph to show the relationship between the two variables. When drawing a line of best fit or trend line it is important to have as many points as possible going through the line.

A strong correlation is when the points on the scatter graph lie very close to the line of best fit. With a strong correlation, the two variables are related to one another - as one changes, so does the other. A weak correlation is when the points lie far away from the line of best fit. In this case, the two variables are not necessarily related to one another - a change in one does not mean a change in the other.

Scatter graph with a line of best fit

Interpolate trends

This is when a value is found within the data set, using the line of best fit. The value was not originally plotted, but can be read off the line of best fit.

Scatter graph with an extrapolation using line of best fit

Extrapolate trends

This is when a value is found outside of the data set. Extrapolation may provide uncertain results as it is based on extending the line of best fit beyond a known set of data.

Scatter graph with an extrapolation beyond line of best fit