To evaluate an application, give a verdict, back it with numbers from the table, and name one thing the evidence leaves out. Use only the evidence supplied.
This lesson is part of space technology within the SPM Science guide. It builds on reading space-technology data.
What do I write, in what order?
Use a three-part routine. State the claim, give the evidence with values, and finish with a limit.
The same routine appears in the claim and evidence revision desk, where you can test your sentences.
Worked example: flood warning for a state
The table is original. A state compares two ways to warn of heavy rain.
| Satellite images | Ground rain gauges | |
|---|---|---|
| Update interval | 30 minutes | 60 minutes |
| Coverage | Whole state | 12 stations |
| Rainfall amount | Estimated | Measured directly |
Claim. Use the satellite images to spot a storm early, and the gauges to confirm how much rain fell.
Evidence. The satellite updates every 30 minutes, twice as often as the gauges, and covers the whole state. The gauges measure the amount directly, but at only 12 stations.
Limit. The table does not say how accurate the satellite estimate is, so the gauges are still needed for the amount.
The mistake that costs marks
The common slip is to bring in outside knowledge, such as a fact about a particular satellite network that is not in the table. It may be true, but the question did not give it as evidence, so it earns no mark.
| Step | Wrong | Right |
|---|---|---|
| Source | What I remember | The table in the question |
| Evidence | “Satellites are very advanced” | “Updates every 30 minutes against 60” |
| Verdict | Satellites are better | Satellite for early warning, gauges for amounts |
| Limit | (missing) | Accuracy of the estimate is not given |
The fix is to point to a cell of the table in every sentence.
A second example: tracking a lorry
A delivery company compares two ways to track a lorry.
| Satellite navigation | Driver phone reports | |
|---|---|---|
| Position update | Every 10 seconds | Every 30 minutes |
| Signal lost in tunnels | Yes | No |
Satellite navigation would show a stopped lorry almost at once, since it updates every 10 seconds. The phone reports could take up to 30 minutes to reveal the stop. The table also shows that the satellite signal is lost in tunnels, which is a limit.
Check yourself
Using only the table above, state which method the company should use to find a stopped lorry quickly, and give one limit.
Answer
Satellite navigation. It updates every 10 seconds, while driver reports come every 30 minutes (1 800 seconds), so it finds a stopped lorry about 180 times sooner in the best case.
Limit: the table says the signal is lost in tunnels, so the tracking has gaps there. The table does not say how long such gaps last.
What to study next
Test the whole cluster with the space technology practice set. If your evidence sentences are vague, return to reading space-technology data.
If you want a teacher to go through your evaluations with you, see online one-to-one Science tuition.