Why (B) is right: confusing correlation with causation
A Flaw explanation from our free library. The question below is original, written for this page. Then the full breakdown: why the right answer is right, and why each wrong answer is wrong.
The question
A recent study found that cities with more bike lanes have lower traffic-accident rates. An editorial concludes that building more bike lanes makes streets safer, and recommends that every city add bike lanes to cut accidents.
The reasoning in the editorial is most vulnerable to criticism on which one of the following grounds?
- It ignores the fact that bike lanes cost money to build and maintain.
- It takes a correlation between bike lanes and accident rates as proof that the bike lanes cause the lower rates. Correct
- It assumes that every city without bike lanes has dangerous streets.
- It relies on accident data that includes all traffic accidents rather than cycling accidents only.
- It fails to consider that bike lanes might slow traffic and make commutes longer.
Why (B) is correct
The study shows two things moving together: more bike lanes and fewer accidents. Moving together is not the same as one causing the other. Maybe bike lanes do help. But the data alone does not prove it.
Wealthier cities may build more bike lanes and also spend more on road maintenance and traffic enforcement. Or cities that already care about safety may do many safe things at once, with bike lanes just one of them. Until the argument rules out these other explanations, the jump from correlation to cause is unjustified. Choice (B) names exactly that jump.
Why the wrong answers are wrong
(A) True but irrelevant
The argument is about safety, not cost. Even if bike lanes are expensive, that does not touch the claim that they make streets safer. A point can be true and still irrelevant to the reasoning.
(C) Misstates the argument
The editorial never claims that cities without bike lanes are dangerous. It claims bike lanes make streets safer. Attacking a claim the argument never made misses the point, and it is stronger than anything the editorial said.
(D) Misses the claim
The conclusion is about overall street safety, so overall accident data is the right evidence. This objection answers a question the argument never asked.
(E) True but irrelevant
Longer commutes do not contradict the claim about safety. The editorial could be right about accidents and silent about commute times at the same time.
Last updated October 12, 2026