A scatter graph or line graph can show a correlation between two variables. In a positive correlation, as one increases the other increases. In a negative correlation, as one increases the other decreases. If the points are scattered with no trend, there is no correlation.
A correlation does not always mean one thing causes the other. Ice-cream sales and sunburn both rise in summer, but ice cream does not cause sunburn: hot sunny weather causes both. In a controlled experiment, where only the independent variable is changed, a correlation is much stronger evidence of cause.
Worked example
As exercise time increases, pulse rate increases. What type of correlation is this?
- Both variables go up together.
- That is a positive correlation.
Answer:It is a positive correlation.
Key words
- correlation
- a link between two variables
- positive correlation
- both increase together
- negative correlation
- one increases as the other decreases
- cause
- makes something happen
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