Recognising Assumptions

Recognising assumptions is a critical skill tested in the UCAT Decision Making subtest. These questions present an argument or statement and ask you to identify the unstated assumption — the hidden premise that must be true for the argument to hold.

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What Is an Assumption?

An assumption is an unstated belief or premise that is taken for granted in an argument. It is the "missing link" between the evidence and the conclusion — something the arguer has not said explicitly but must believe for their argument to work.

The Structure of an Argument

Every argument has:

1. Evidence / Premises — the stated facts or reasons
2. Conclusion — what the arguer claims follows from the evidence
3. Assumptions — the unstated premises needed to connect the evidence to the conclusion

Example:

• Evidence: "Medical school applications have increased by 20% this year."
• Conclusion: "There will be more doctors in the NHS in five years' time."
• Assumption: Applicants will be accepted, complete their training, and choose to work in the NHS. (This is unstated but necessary for the conclusion to follow.)

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Distinguishing Assumptions from Other Elements

Students often confuse assumptions with conclusions, evidence, or implications. Here is how to distinguish them:

Element	Definition	Key Question
Evidence	Stated facts used to support the argument	"What reasons are given?"
Conclusion	The claim being made	"What is the arguer trying to prove?"
Assumption	Unstated premise needed for the argument	"What must be true for this argument to work?"
Implication	Something that follows from the conclusion	"If the conclusion is true, what else would be true?"

An assumption is not stated in the passage. If it is stated, it is evidence, not an assumption.

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The Negative Test for Assumptions

The most reliable method for identifying assumptions is the negative test (also called the "assumption negation test"):

How It Works

1. Take the proposed assumption
2. Negate it (assume it is false)
3. If the argument falls apart when the assumption is negated, then it IS an assumption of the argument
4. If the argument still works when the assumption is negated, then it is NOT an assumption

Worked Example

Argument: "The hospital should hire more nurses because patient satisfaction surveys show that patients value having more time with nursing staff."

Proposed assumption: "Patient satisfaction surveys accurately reflect what patients value."

Negative test: Suppose patient satisfaction surveys do NOT accurately reflect what patients value. Then the evidence (surveys show patients value nursing time) is unreliable, and the argument collapses.

Result: This IS an assumption of the argument. ✓

Alternative proposed assumption: "Nurses are more important than doctors."

Negative test: Suppose nurses are NOT more important than doctors. The argument is about hiring more nurses based on survey evidence — it does not depend on nurses being more important than doctors. The argument still works.

Result: This is NOT an assumption of the argument. ✗

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Common Types of Assumptions in UCAT Questions

Type 1: Causal Assumptions

The argument assumes that one thing causes another.

Example:

• Evidence: "Students who attend revision classes score higher in exams."
• Conclusion: "Revision classes improve exam performance."
• Assumption: "The higher scores are caused by the revision classes, not by other factors (e.g., more motivated students are more likely to attend revision classes AND score higher)."

Type 2: Generalisation Assumptions

The argument assumes that what is true for a sample is true for a wider population.

Example:

• Evidence: "A survey of 50 patients at one hospital found that 80% preferred afternoon appointments."
• Conclusion: "Most patients prefer afternoon appointments."
• Assumption: "The 50 patients surveyed are representative of patients in general."

Type 3: Implementation Assumptions

The argument assumes that a proposed action is practically feasible.

Example:

• Evidence: "Studies show that exercise reduces depression."
• Conclusion: "GPs should prescribe exercise instead of medication for depressed patients."
• Assumptions: "Depressed patients are able to exercise," "Exercise is as effective as medication for clinical depression," "Patients will comply with exercise prescriptions."

Type 4: Value Assumptions

The argument assumes that a particular value or priority is more important than alternatives.