An assumption, in GMAT Critical Reasoning questions, is an unstated premise. It’s a piece of evidence necessary for the conclusion to logically follow from the stated premises It represents a gap, missing link, or shift in scope between the premises the author cites and the conclusion the author reaches.
Almost all GMAT passages will have at least on assumption. Some passages will feature questionable reasoning, relying on multiple unsupportable assumptions. Others may be logically valid, relying only on assumptions that are reasonable to make.
In some cases you will need to find the assumption yourself. Fortunately, many other arguments follow frequently repeated patterns. Identifying those common argument structures will let you answer considerably faster.
Example: The law requires a prescription to purchase narcotic drugs. Therefore, Cerulex requires a prescription to purchase.
The premise is the first sentence about the law on narcotic drugs. The conclusion is about the drug Cerulex. The law only affects narcotic drugs, so in order for the law to affect Cerulex, Cerulex must be a narcotic. Since this fact is necessary, but omitted, it’s an assumption.
Assumption question ask specifically for the author’s assumptions. Look for gaps in the argument, changes of topic between premise and conclusion, and commonly repeated argument structures. Once you’ve identified the assumption, go straight to the answer choices and look for a match.
Squeepees are a type of small pig that, if infected with ululalia, will scream at changes in ambient temperature. Therefore, those who own infected squeepees will suffer an earsplitting racket every time it rains.
The conclusion drawn above is based on the assumption that:
Correct Answer: Rain is always accompanied by a change in ambient temperature.