Unit 6 · Identifying Sufficient Information
Window Cleaning Ad — Which Facts Are Enough?
Lesson 1 of 3
Sufficient-information questions ask what you must know to test a claim — not what is merely helpful or related.
Claim-testing tables appear on Selective TS when an ad or statement needs evidence; they reward students who separate “nice to know” from “proves or disproves the claim.”
The examiner checks whether you can design a fair test: for each case you need to know if the treatment was used and whether the outcome happened — so you can compare like with like.
A bold claim is made (e.g. a product works in under four wipes). A table lists trials with missing answers (a), (b), (c). You pick which missing facts are essential to test the claim.
Best approach: State the claim precisely. For a fair test you usually need both “was the method used?” and “did the result occur?” on each row. Eliminate facts that do not pin down success vs failure or used vs not used.
Question
An advertisement for a window cleaning spray claimed: Spray cleans window in less than 4 wipes. Four windows were cleaned and 2 questions were asked in each case:
| Room | Was the window spray used? | Did it clean in less than 4 wipes? |
|---|---|---|
| 1 | Yes | (a) |
| 2 | (b) | Yes |
| 3 | No | (c) |
| 4 | (d) | No |
Which two of the missing answers must be known in order to test the truth of the claim in the advertisement?
Select an answer to see the explanation.
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