These are original Marlbridge practice questions, not past exam questions. The three sources below are fictional, written by Marlbridge for this resource. The rubrics are a suggested Marlbridge rubric, not an official scoring guideline. Allow about 50 minutes.
The issue: Do households need to buy water filters?
Source G (brochure from a water-filter company, fictional): “In a survey of 50 visitors to our stand at the town fair, 9 in 10 said our filtered water tasted better than tap water. Tap water is full of impurities that only our filter removes. Isn’t it time your family drank clean water?”
Source H (report by an independent consumer group, fictional): “We tested tap water samples from 120 homes in the region and compared them with three brands of home filter. All samples met the national safety standard. Filters improved taste scores in blind tests by a small margin, but the difference was not significant for most testers. The tests were carried out over two weeks in spring.”
Source I (letter from the regional water company, fictional): “Our water is tested daily and meets all safety standards. Complaints about taste are rare. We do not recommend that households buy filters for safety reasons.”
Question 1 (multiple choice · core)
Which feature of Source G is the clearest sign of bias?
- (A) It mentions a survey.
- (B) It is produced by a company that sells filters, uses the loaded phrase “full of impurities” and does not consider other views.
- (C) It uses numbers.
- (D) It was published at a town fair.
Answer and explanation
Answer: (B). Interest, loaded language and omission of other views are the classic signs of bias.
- (A) Mentioning a survey is not bias; the question is how the survey was done.
- (C) Numbers are not a sign of bias.
- (D) The setting is a limitation of the sample (see Question 2), not evidence of bias in itself.
Question 2 (multiple choice · core)
Which of the following is a limitation of the evidence in Source G, as distinct from bias?
- (A) The survey asked only 50 visitors to the company’s own stand, so its sample is small and self-selected.
- (B) The brochure is written by a company.
- (C) The brochure asks a rhetorical question.
- (D) The brochure uses the word “clean”.
Answer and explanation
Answer: (A). A small, self-selected sample restricts what the survey can show, even if the company were scrupulously fair.
- (B) is a sign of interest, which relates to bias.
- (C) is a rhetorical device that relates to bias.
- (D) is a loaded word, again a sign of bias.
Question 3 (multiple choice · core)
Which source does most to consider other positions, and what does that suggest about its bias?
- (A) Source G, because it uses a survey; it is the least biased.
- (B) Source H, because it reports both the filters’ small benefit and the tap water’s safety; it shows the least bias of the three.
- (C) Source I, because it comes from the water company; it is the least biased.
- (D) All three equally, because each mentions water.
Answer and explanation
Answer: (B). Source H presents findings that cut in different directions and describes its method, so it considers other positions most fully.
- (A) Source G does not consider other views, and its survey is self-selected.
- (C) Source I has an interest and offers no data.
- (D) The three sources differ greatly in how fairly they treat other views.
Question 4 (multiple choice · core)
Which sentence uses Source G most responsibly?
- (A) A survey shows that 9 in 10 people prefer filtered water, so tap water is poor.
- (B) A filter company reports that 45 of 50 visitors to its stand preferred its filtered water, but the sample is small and self-selected, so the figure says little about tap water in general.
- (C) Source G is biased, so it should be ignored.
- (D) Filtered water is obviously better because the brochure says so.
Answer and explanation
Answer: (B). It states the claim accurately (9 in 10 of 50 is 45), names the interest and the limits, and says what the evidence cannot show.
- (A) overstates: the survey was of 50 stand visitors and did not test tap water quality.
- (C) dismisses the source without using it; a biased source can still show what a company claims.
- (D) treats an interested claim as fact.
Question 5 (multiple choice · foundation)
Which statement about bias is most accurate?
- (A) Bias means a source contains false statements only.
- (B) Bias is a leaning that distorts how a source presents its subject, and the degree to which a source considers other positions reflects its degree of bias.
- (C) Every source with a position is equally biased.
- (D) A source cannot be both useful and biased.
Answer and explanation
Answer: (B). This captures the idea of distortion and the measure of consideration of other positions.
- (A) A biased source may contain only true statements but present them one-sidedly.
- (C) Bias is a matter of degree.
- (D) A biased source can still be useful if its bias is acknowledged.
Question 6 (constructed response · core)
Source I is from the water company. Explain what Source I can and cannot be used for in an argument, and how you would introduce it.
Answer and explanation
Sample response. Source I can be used as evidence of the water company’s position and of what it says about its own testing: that it tests daily and meets standards. It cannot be used as neutral proof that the water is safe, because the company has an interest in households trusting its supply and gives no figures. A writer could introduce it as: “The regional water company states that its water is tested daily and meets all safety standards, though the company offers no figures and has an interest in households trusting its supply.” This should be paired with independent evidence, such as Source H, which found that all 120 samples met the national standard.
Suggested Marlbridge rubric (4 points).
| Point | Award it when the response… |
|---|---|
| 1 | States what the source can show (the company’s claim) |
| 1 | States what it cannot show (neutral proof) and why (interest, no data) |
| 1 | Models an introduction that signals the interest |
| 1 | Suggests pairing it with independent evidence |
Question 7 (constructed response · core)
Compare the reliability of Sources G, H and I as evidence about whether households need filters. Refer to bias and limitations, and rank them.
Answer and explanation
Sample response. Source H is the most reliable: it is independent, reports a method (120 homes, blind taste tests), and presents findings that complicate any simple claim (tap water met standards, filters gave a small taste benefit). Its limits are that it covers one region over two weeks in spring. Source I ranks next: the water company has an interest and gives no figures, but it makes a modest claim (safety standards are met) that Source H independently supports. Source G is the least reliable: a filter company’s survey of 50 visitors to its own stand is small and self-selected, measures taste only, and its claim that tap water is “full of impurities” is not supported by its own evidence.
Suggested Marlbridge rubric (5 points).
| Point | Award it when the response… |
|---|---|
| 1 | Ranks H as most reliable with a reason |
| 1 | Identifies H’s limitation (region, season, duration) |
| 1 | Identifies I’s interest and lack of data |
| 1 | Identifies G’s interest, sample limitations and unsupported claim |
| 1 | Uses the idea of consideration of other positions (or independence) as a criterion |
Alternative rankings (G above I) may be credited if justified by the evidence.
Question 8 (constructed response · stretch)
Write a paragraph of five to seven sentences that argues households do not need filters for safety, using Sources G, H and I. Acknowledge at least one bias and one limitation, and adjust your claim to match the evidence.
Answer and explanation
Sample response (Marlbridge).
Households appear not to need filters for safety, although they may reasonably choose them for taste. An independent consumer group found that all 120 tap-water samples it tested met the national safety standard, and the regional water company says the same, though as the supplier it has an interest in saying so and offers no figures. The one source that criticises tap water, a filter company’s brochure, rests on a survey of 50 people at its own stand, a small and self-selected group that was asked about taste, not safety. The consumer group’s blind tests found only a small taste benefit from filters, and the study covered one region over two weeks, so its results may not hold everywhere. The evidence therefore supports a limited claim: tap water in this region is safe, and a filter is a matter of preference, not need.
Suggested Marlbridge rubric (5 points).
| Point | Award it when the response… |
|---|---|
| 1 | States a claim that matches the evidence (qualified) |
| 1 | Uses Source H as the main evidence, accurately |
| 1 | Acknowledges a bias (company interest) |
| 1 | Acknowledges a limitation (sample, scope, method) |
| 1 | Avoids overclaiming and ends with a conclusion that follows |
How did you do?
- If you missed questions 1, 3 or 5, revisit “Bias” in the study guide.
- If you missed questions 2 or 4, review “Limitations” and “Acknowledging and accounting for limitations”.
- If you missed questions 6 to 8, review Worked examples 1 and 2.
- Then tick off the checklist and revise with the revision notes.