Line graphs
Line graphs display data where both variables are continuous.
The table shows some data for alcohol-related deaths in females in England and Scotland between 2015 and 2022.
| Year | England | Scotland |
| 2015 | 10.3 | 19.5 |
| 2016 | 10.5 | 21.1 |
| 2017 | 11.1 | 20.5 |
| 2018 | 10.7 | 20.8 |
| 2019 | 10.8 | 18.5 |
| 2020 | 13 | 21.5 |
| 2021 | 13.9 | 22.3 |
| 2022 | 14.5 | 22.6 |
| Year | 2015 |
|---|---|
| England | 10.3 |
| Scotland | 19.5 |
| Year | 2016 |
|---|---|
| England | 10.5 |
| Scotland | 21.1 |
| Year | 2017 |
|---|---|
| England | 11.1 |
| Scotland | 20.5 |
| Year | 2018 |
|---|---|
| England | 10.7 |
| Scotland | 20.8 |
| Year | 2019 |
|---|---|
| England | 10.8 |
| Scotland | 18.5 |
| Year | 2020 |
|---|---|
| England | 13 |
| Scotland | 21.5 |
| Year | 2021 |
|---|---|
| England | 13.9 |
| Scotland | 22.3 |
| Year | 2022 |
|---|---|
| England | 14.5 |
| Scotland | 22.6 |
Plotting the graph for England (green line) and Scotland (red line) so that the data can be compared.
With line graphs, you have a choice between connecting the plots point-to-point, or using a line of best fit.
Joining dots point to point is essential to show fluctuations in data - for instance, with the death rates - above - or a person's body temperature. Data points can be connected point to point when there is confidence in their quality.
A line of best fit looks at how variables behave in relation to each other - it is used to establish or display a correlation or a trend. These relationships may not be obvious from a table of data or could be obscured by experimental errors. Lines of best fit are also used to make predictions.
Question
In the graph above, the population of which country shows the most fluctuation in the number of alcohol-related deaths?
Scotland is the country whose population shows the most fluctuation in the number of alcohol-related deaths.
Question
If the data for 2022 is:
England: alcohol-related death rate = 14.5 per 100,000 of population
Scotland: alcohol-related death rate = 22.6 per 100,000 of population
What has happened to the number of deaths for each country between 2021 and 2022?
England’s has risen and Scotland’s roughly stayed the same.
Instead of simply describing what has happened Results that are not expressed as numbers or numerical data, eg they can be expressed as present or absent, or as colours., you could make your analysis Results that can be expressed using numerical values., to give more information.
In England, deaths rose by 60,000.
That's 14.5 − 13.9 = 0.6 × 100,000 = 60,000.
