To evaluate a claim, compare what the claim says with what the evidence actually shows, then state a judgement and its limits. In biotechnology questions, the claim is often about yield, safety, cost or speed, and the data only cover part of it.
This lesson uses skills that are trained more widely in Biology data and investigations.
A four-step method
- Quote the claim. Write it in your own words.
- List what was measured. Yield, growth, mass, cost, time.
- Check the data. Calculate means, differences or percentages, and look for a fair comparison.
- State the limit and the judgement. What is supported, what is untested?
Worked example
The trial is invented for practice. A company claims: “Our GM maize increases yield by 20% and is safe for the environment.” A trial grew both types of maize on four plots each, in one field, in one season. Yields in tonnes per hectare:
| Plot | GM maize | Non-GM maize |
|---|---|---|
| 1 | 5.8 | 5.0 |
| 2 | 6.2 | 5.2 |
| 3 | 6.0 | 4.8 |
| 4 | 6.4 | 5.0 |
Question: Evaluate the claim.
Step 1, means. GM: (5.8 + 6.2 + 6.0 + 6.4) ÷ 4 = 24.4 ÷ 4 = 6.1 t/ha. Non-GM: (5.0 + 5.2 + 4.8 + 5.0) ÷ 4 = 20.0 ÷ 4 = 5.0 t/ha.
Step 2, percentage increase. (6.1 − 5.0) ÷ 5.0 = 1.1 ÷ 5.0 = 0.22, so 22%.
Step 3, judge the yield part. The data support a yield increase of about 22%, which is slightly above the 20% claimed. Every GM plot gave more than every non-GM plot, so the pattern is consistent.
Step 4, judge the safety part. No measurement of environmental effects was reported, so the trial gives no evidence for “safe for the environment”.
Step 5, limits. Only four plots, one field and one season, so the result may not hold elsewhere or in other years.
Conclusion: The yield claim is supported for this field and season. The safety claim is not supported by this evidence.
The mistake to watch for
Mistaken answer: “The trial proves GM maize is better and safe.”
“Proves” is too strong. The trial measured yield only, in one place for one season. A judgement should match the strength of the evidence, for example “supports a higher yield in this trial”.
The correction is to add a limit to every conclusion: which measure, which conditions, and what remains untested.
Check yourself
1. GM plots give a mean yield of 4.5 t/ha and non-GM plots 3.6 t/ha. Calculate the percentage increase.
Show answer
4.5 − 3.6 = 0.9. 0.9 ÷ 3.6 = 0.25. So 25%.
2. A claim says a crop is “healthier to eat”. The trial recorded only plant height. Is the claim supported?
Show answer
No. Plant height says nothing about the nutritional value or effects of eating the crop, so the evidence does not address the claim.
3. Name two ways to make the maize trial above more convincing.
Show answer
Any two: more plots or repeats, several fields or locations, more than one season, and measuring other outcomes such as effects on nearby species.
Where this leads next
Finish with the biotechnology practice set, which mixes this skill with the earlier lessons. You can revisit gene insertion and selective breeding if you want to compare the methods the claims are about.
Evaluation is easier when a teacher reads your draft and asks “what did they actually measure?” in real time, and that is what online one-to-one Biology tuition offers. The full lesson list is on the module page.