This deep dive covers Drawing Lines of Best Fit within Scatter Graphs for GCSE Mathematics. Revise Scatter Graphs in Statistics for GCSE Mathematics with 14 exam-style questions and 20 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 5 of 8 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Drawing Lines of Best Fit
Method for Drawing the Line
- Plot all points accurately on the graph
- Ignore outliers when considering the trend
- Draw a straight line that best represents the trend
- Balance the line so roughly equal numbers of points are above and below
- Make the line long enough to be useful for predictions
Using Lines of Best Fit for Predictions
Interpolation
Predicting values within the range of your data.
Example: If the line shows that 5 hours study gives 75% score, this is interpolation.
Extrapolation
Predicting values outside the range of your data.
Example: Using the line to predict what score someone would get with 12 hours study (if your data only goes up to 10 hours).
Warning: Extrapolation is less reliable - relationships may change outside the measured range.
Practice questions for Scatter Graphs
A scatter graph shows that as temperature increases, ice cream sales also increase. This is an example of:
A scatter graph shows a strong positive correlation between the number of ice creams sold and the number of drowning incidents at a beach. A student says: 'Ice cream causes drowning.' Explain why this conclusion is incorrect.