Scatter diagrams and correlation
Scatter diagrams and correlation
- A scatter diagram plots pairs of values to show whether two things are linked. The link is the correlation:
- positive — as one goes up, the other goes up.
- negative — as one goes up, the other goes down.
- zero — no clear link.
Practice
As one quantity increases, the other also increases. This is:
Both rising together is positive correlation.
Practice
Negative correlation means as one quantity goes up, the other goes down.
A downward trend on the scatter diagram is negative correlation.
Line of best fit
- If there is correlation, draw one straight ruled line through the middle of the points, roughly equal numbers each side.
- Use it to predict values.
Practice
A line of best fit is mainly used to:
It models the trend so you can predict one value from the other.
You've got it
Key idea
- positive correlation rises together; negative falls as the other rises; zero = no link
- a line of best fit is one straight line through the middle of the points
- use the line to predict — but don't trust it far outside the data