THINKING FOUNDATIONS
Evidence and inference
Separate what was observed from what is claimed, what would support the claim, what is being assumed, and what conclusion is actually allowed. Correlation is not, by itself, causation.
1. Everyday example
Everyday: ice cream and sunburn
People buy more ice cream on days when more people are sunburned. That is a correlation. The observation does not show that ice cream causes sunburn. A shared cause, sunshine, is a rival inference. The claim “ice cream burns skin” is bigger than the evidence.
2. A level example
A level: a graph and a conclusion
A graph can show that as nitrate in a stream increases, invertebrate diversity falls. That is the observation. “Nitrate kills the invertebrates” is an inference. It may be right, but the graph has not ruled out sewage, temperature or sampling bias. Say what the evidence supports, and name the assumption if you go further.
3. Show me
Show me. Sort one illustrative study into the right kinds of statement.
- Observation: the mean yield was higher in the fertilised plot.
Following the sequence is practice. It is not recorded as mastery.
4. Guide me
Practice question
Guide me. Two variables rise together on a graph. Which response treats correlation carefully?
5. Let me try
Independent transfer. My Progress records this only when the reasoning holds.
Practice question
Let me try. A question gives a zone of inhibition wider than a water control on one plate. Which inference is supported?