GMAT Critical Reasoning: strengthen a causal argument
A Strengthen question asks which additional information makes the conclusion better supported. The correct answer can introduce a new fact. It need not prove the conclusion or match a single assumption you predicted before reading the choices.
Original example: did the alerts cause the improvement?
A fictional transit operator introduced real-time alerts on Route A. Passenger satisfaction rose after the change. The operator concludes that the alerts contributed to the rise.
Which statement, if true, most strengthens that conclusion?
- Satisfaction rose just as much on similar routes without alerts.
- Riders randomly assigned access to the alerts reported higher satisfaction than riders without access during the same period, while fares and service conditions were otherwise the same.
- The operator plans to install alerts on more routes.
- The alerts use a new typeface.
- The route’s timetable is available online.
Answer: B. The comparison provides evidence for an effect of access to the alerts while reducing alternative explanations from service conditions or systematic group differences. It strengthens the causal claim; it does not establish that alerts explain every change in satisfaction.
A points toward a shared explanation across routes. C describes a plan, not its effectiveness. D and E do not connect the alerts with the reported improvement.
A careful way to compare answers
- Identify the conclusion and the evidence already given.
- Ask what alternative explanations or missing links matter.
- Treat each answer as true, as the question instructs.
- Compare how directly it supports this conclusion.
Do not automatically reject a choice because it adds evidence for a premise. Depending on the argument, that can strengthen the conclusion. Likewise, showing that a trend was absent in an earlier year does not rule out every new competing cause.
Practise the actual Verbal task
GMAT Verbal includes Critical Reasoning and Reading Comprehension; avoid assuming a fixed published proportion of Strengthen questions. Use official practice and explain why each alternative has a different effect on the argument.
For online GMAT tutoring from Paris, bring the argument and your rejected options. They make the lesson more specific than a general request for a Verbal score increase.