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Strengthening and Weakening Arguments: Find the Gap First

Conclusion and premise • The hidden gap • Alternative causes • Unrepresentative samples • Out-of-scope options

Banking UPSC 📅 Last updated: 2026-10-24

These questions give a short argument and ask which option, if true, most strengthens or most weakens it. They appear in bank mains reasoning and in the comprehension portion of the UPSC CSAT paper. The method is the same for both.

Every argument has a conclusion, the claim being made, and one or more premises, the evidence offered for it. Between them sits a gap: something the author takes for granted so that the evidence leads to the claim. Strengthening and weakening questions are almost always about that gap.

Worked example 1: finding the gap

'Since the city built bicycle lanes, the share of commuters cycling to work has risen from 4% to 6%. So the lanes have encouraged cycling.'

Conclusion: the lanes encouraged cycling. Premise: cycling rose after the lanes were built. Gap: the rise was caused by the lanes and not by something else. The rise is 2 percentage points, which is a 50% increase in the share of cyclists.

Notice the two ways of describing that rise. A question might quote either one; read options with numbers carefully before deciding which figure they refer to.

A weakener attacks the gap, not the premise. Accept the evidence and show that it does not lead to the conclusion. The commonest ways:

  • An alternative cause: something else explains the evidence. If fuel prices doubled during the same period, people may have taken up cycling to save money, lanes or no lanes.
  • A broken assumption: the argument needs something that turns out to be false.
  • An unrepresentative sample: the evidence comes from a group that is not typical of the people the conclusion is about.

Worked example 2: an unrepresentative sample

'Of 200 students surveyed at one coaching centre, 160 said they prefer evening batches. So most students in the state prefer evening batches.'

That is 80% of the sample, but students at one centre may share timetables, jobs or travel patterns that the state's students do not. An option showing that most of them work during the day would weaken the argument sharply.

A strengthener closes the gap. It confirms the assumption, rules out an alternative cause, or adds a comparison that isolates the claimed cause.

Worked example 3: a comparison group

For the bicycle-lane argument, the strongest support would be: 'Cycling rose only on routes with new lanes and stayed flat on routes without them.' The comparison rules out city-wide causes such as fuel prices or weather, leaving the lanes as the likely cause.

Worked example 4: confirming the assumption

'The bank should open a branch in the new township, because thousands of families have moved there.' The gap: these families will use a local branch. An option saying most of them currently travel over 10 km to bank confirms that the need is real and strengthens the argument.

Many wrong options are simply about something else. They may be true, positive or interesting, yet have no bearing on whether the evidence supports the conclusion. Typical examples: details of how the plan works, people's opinions about it, or future plans. Before choosing an option, say in one sentence how it affects the gap. If you cannot, it is out of scope.

Watch, too, for options that weaken when you are asked to strengthen, and the reverse. Underline the word strengthen or weaken in the question; it is easy to lose track halfway through a long set.

  1. Read the question line first, so you know whether you are strengthening or weakening before you read the argument.
  2. Mark the conclusion. It often follows words such as so, therefore, thus or hence.
  3. Name the gap in a few words, for example 'the lanes, not something else, caused the rise'.
  4. Predict the answer before reading the options: an alternative cause, a comparison, or a fact about the sample.
  5. Test each option against the gap, and pick the one with the biggest effect, not merely one with some effect.

Predicting before reading the options is the easiest step to skip under time pressure, and it is the one that protects you from attractive but irrelevant choices.

  • ✘ Doubting an option instead of accepting it as true.
  • ✘ Attacking the premise instead of the link between premise and conclusion.
  • ✘ Choosing an option that is about the topic but not about the gap.
  • ✘ Mixing up percentage-point changes with percentage changes.

Related topics: statement and assumptions (finding the gap), cause and effect (alternative causes) and strong and weak arguments.

Q1. Argument: 'Students who attend the optional evening classes score higher in the final exam than those who do not. So the evening classes improve exam scores.' Which of the following, if true, most weakens the argument? medium

✅ Answer: (a) Students who attend the evening classes were already the top scorers before they joined

💡 Explanation: If the attendees were already the strongest students, their higher scores may have nothing to do with the classes. That is an alternative explanation. A few good scorers among non-attendees does not affect the average comparison.

Q2. Argument: 'After a town installed streetlights in its market area, reported thefts there fell from 50 to 30 a year. The streetlights reduced theft.' Which of the following, if true, most strengthens the argument? medium

✅ Answer: (b) In areas of the town without new lights, thefts stayed the same over the period

💡 Explanation: Thefts fell by 40% in the market. If similar areas without lights saw no fall, the change is more likely due to the lights. A state-wide fall would point to some other cause and weaken the argument.

Q3. Argument: 'Company X's monthly sales rose from 100 to 120 thousand units in the month after its TV advertisement began. Therefore the advertisement increased sales.' Which of the following, if true, most weakens the argument? easy

✅ Answer: (c) X's main competitor stopped selling that month because of a factory fire

💡 Explanation: Sales rose by 20%, but if the main competitor vanished that month, its customers had to buy elsewhere. That alternative cause could explain the rise without the advertisement.

Q4. Argument: 'Online coaching classes will help rural students prepare for competitive exams, so the state should fund them.' Which of the following, if true, most strengthens the argument? medium

✅ Answer: (d) Most rural students in the state have mobile internet access

💡 Explanation: The argument assumes rural students can reach the online classes. Confirming that most have internet access supports that assumption. The other options are about urban students, fees or teachers' tastes.

Q5. Argument: 'In a survey of 400 members of a gym, 300 said they would buy protein bars. So most people in the city would buy protein bars.' Which of the following, if true, most weakens the argument? easy

✅ Answer: (a) Gym members are far more interested in protein products than the general public

💡 Explanation: 75% of gym members said yes, but gym members are not typical of the whole city. If they are much keener on protein products, the sample cannot support a claim about most people.

Q6. Argument: 'Since the new metro line opened, traffic on the parallel highway has fallen by 15%. So the metro has reduced road traffic.' Which of the following, if true, most weakens the argument? medium

✅ Answer: (b) Part of the highway was closed for repairs during the same period

💡 Explanation: A partial closure would push traffic off the highway regardless of the metro, which is an alternative cause. Rising ridership and riders switching from highway buses both support the argument instead.

Should I check whether an answer option is actually true?

No. These questions say 'if true', so accept each option as a fact and ask only how it affects the argument. Whether the option is realistic or matches the news does not matter.

What is the difference between a strengthener and the assumption itself?

The assumption is the unstated link the argument needs. A strengthener is any new fact that makes that link more likely, such as ruling out another cause. In practice, an option that confirms the assumption is usually the strongest strengthener.

All problems and solutions on this page are original. No outside facts are relied on; every numeric answer is recomputed by software before publishing.

How this page was prepared. Drafted with AI assistance (Claude (Anthropic AI model)) from the sources listed above. 6 calculations on this page were recomputed by software and matched. Automated checks also covered structure, internal links and duplicate text. Software checks cannot confirm facts. Reviewed by praveenkumar on 2026-10-24 against the sources listed above.

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