Inference vs Assumption in CAT RC: The Difference, With Examples
Inference and assumption sound alike and trip up even strong readers. One comes after the argument, the other holds it up from below. Here is how to tell them apart in seconds.
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Many CAT aspirants lose marks on questions they understood. They read the passage well, but chose an option that was an assumption when the question asked for an inference, or the other way round. The two words are used loosely in daily life. In CAT RC and critical reasoning they mean precise, different things.
The one-line difference
An inference is something that must be true because of what the passage says. It sits downstream of the argument. An assumption is something the author must take for granted for the argument to work, but never states. It sits upstream, holding the argument up.
| Inference | Assumption | |
|---|---|---|
| Where it sits | After the argument: a conclusion you can draw | Before the argument: an unstated premise |
| Stated in the passage? | No, but it must follow from what is stated | No, and the argument needs it |
| Test | Is it necessarily supported by the text? | If it were false, would the argument collapse? |
| Typical question wording | 'It can be inferred that', 'The passage implies' | 'The author assumes', 'The argument depends on' |
A worked example
Passage: 'Since the city introduced free buses, car traffic in the centre has fallen by a fifth. The policy should therefore be extended to the suburbs.'
A valid inference: some people who used to drive into the centre now use another way to travel. This must be true if traffic fell, and the passage gives us that.
The author's assumption: the fall in traffic was caused by the free buses, and not by something else such as a fuel price rise or road closures. The author never says this, but the recommendation collapses without it. A second assumption: what worked in the centre will work in the suburbs.
The negation test for assumptions
To check whether an option is an assumption, negate it and see whether the argument survives. 'The fall in traffic was not caused by the free buses.' Now the recommendation to extend the scheme has no support. That is how you know it was a necessary assumption.
For an inference, ask the opposite question: could this option be false while everything in the passage stays true? If yes, it is not a valid inference, however reasonable it sounds.
The four traps in CAT options
- The reasonable outsider: a sensible statement the passage never supports. Common in inference questions.
- The extreme version: 'always', 'only', 'never', 'all'. The passage supports a weaker claim, not this one.
- The restatement: in an assumption question, an option that repeats something the author already said is not an assumption, because assumptions are unstated.
- The helpful but unnecessary premise: it would strengthen the argument, but the argument does not need it. It fails the negation test.
How often do these appear in CAT?
Inference questions are among the most common RC question types in recent CAT papers, usually one or two per passage. Pure assumption questions are rarer in RC, and appear more in critical reasoning-style questions and in strengthen or weaken questions, which rely on the same skill: finding the hidden premise.
How to practise
- After every RC set, label each question as inference, assumption, tone, main idea or detail before you check answers.
- For every inference option you rejected, write the one word in the passage that rules it out.
- For every assumption option, apply the negation test out loud.
- Do this on real CAT passages first: the solved CAT RC PYQs show which option traps the IIMs actually use.
Practise on free solved CAT RC PYQs, try a full daily CAT RC passage, or test yourself in a timed CAT VARC mock.
Frequently asked questions
What is the difference between inference and assumption in CAT RC?
An inference must follow from what the passage states; it sits after the argument. An assumption is an unstated premise the argument depends on; it sits before the argument. Test assumptions by negating them: if the argument collapses, it was an assumption.
How do I identify an inference question in CAT?
Look for wording such as 'it can be inferred', 'the passage implies' or 'the author would most likely agree'. The right answer must be supported by the text and cannot be false if the passage is true.
How do I identify an assumption question in CAT?
Look for 'the author assumes', 'the argument depends on' or 'which of the following is presupposed'. The right answer is unstated, and negating it breaks the argument.
Are assumption questions common in CAT RC?
Less common than inference questions. They appear more in critical reasoning-style and strengthen or weaken questions, which use the same skill of finding the hidden premise.
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