Use only what the study measured
- The idea
- Predict
- See it
- Why
- Check
The idea
“A sensible explanation is a fine answer, even if the study never measured that factor.”
Predators, disease and pollution really do change results, so it's tempting to name one the study never measured.
The short version
The mistake: A sensible explanation is a fine answer, even if the study never measured that factor.
What's actually true: A conclusion has to come from the variables the study recorded. The data can't support a factor nobody measured.
- Before you explain a result, list what was measured. Anything else is a guess.
- A strong answer links the measured variables. Dissolved oxygen is the O2 in water that fish take up through their gills.
- An unmeasured factor might be real, but the study can't show that it changed. On the exam, a choice that adds one is usually a trap.
On the exam: Point to the column or axis your answer uses. If you can't, the data can't support it.