To evaluate a claim, state the criterion, test the claim against the supplied numbers and give a verdict: supported, partly supported or not supported. Then add one limit.
This lesson is the last in SPM Science green technology. It uses the table skills from comparing energy choices using supplied data.
What are the four steps?
- Copy out the claim and the criterion.
- Find the numbers that relate to the claim.
- Calculate the quantity the claim is about.
- Give the verdict and name one limit.
The same steps work for a lamp, a bin or a water system.
Worked example: a lamp label
The box for lamp X says two things: “Uses over 80% less energy than an old 60 W lamp” and “Lasts 10 times longer”. The data supplied are below.
| Lamp | Power (W) | Lifetime (hours) |
|---|---|---|
| Old lamp | 60 | 1 000 |
| Lamp X | 9 | 8 000 |
Claim 1, energy. Energy over 1 000 hours: old lamp 60 × 1 000 = 60 000 Wh = 60 kWh. Lamp X: 9 × 1 000 = 9 000 Wh = 9 kWh.
The saving is 60 − 9 = 51 kWh. As a percentage, 51 ÷ 60 × 100 = 85%. Since 85% is above 80%, the claim is supported.
Claim 2, lifetime. 8 000 ÷ 1 000 = 8 times, not 10 times. The claim is not supported: the lamp lasts 8 times longer, which is still a large gain but not the stated 10.
Write the verdict in full
A full answer for claim 1 reads: “The claim is supported. Lamp X uses 9 kWh in 1 000 hours compared with 60 kWh, a saving of 85%, which is more than 80%.”
For the overall product, a careful answer adds a limit: “The data do not include the energy used to make the lamp, so the claim that the lamp is better for the environment overall is not fully tested.”
The mistake that costs marks
The usual slip is to agree with the label without calculating. A student writes “the claim is true because LED lamps are green”, which uses general knowledge and skips the numbers.
| Step | Wrong | Right |
|---|---|---|
| Evidence | LED lamps are green | 9 kWh against 60 kWh in 1 000 hours |
| Claim 2 | Supported, it lasts much longer | Not supported, 8 times not 10 times |
| Limit | Not given | Manufacturing energy is not in the data |
The fix is to calculate the figure named in the claim, then compare it with the figure in the claim, not with your general impression.
Check yourself
A tap fitting claims: “Saves at least half the water.” Before fitting, a sink used 12 litres a minute. After fitting, it uses 7 litres a minute. Evaluate the claim.
Answer
The saving is 12 − 7 = 5 litres a minute. As a percentage, 5 ÷ 12 × 100 = about 42%.
Half is 50%, so the claim is not supported: the fitting saves about 42%, which is a real saving but below half. A limit is that the flow rate may change with water pressure at different buildings.
What to study next
Test all four skills in the green technology practice set. For the general habit of judging data, read evaluating a science claim from a supplied dataset.
The graph evidence and fair-comparison lab offers extra tables. If you want a teacher to go through your verdicts, see online one-to-one Science tuition.