LSAT Weaken Practice Question: Causal Flaw
An original weaken question from our free Question of the Day rotation, built around a trap the LSAT reuses constantly: causal flaw. Try it first, then read the explanation — it teaches the move, not just the answer.
Your job:Make the conclusion less believable.
The Marlow Bay ferry company repainted its aging boats bright yellow in early April. In May, ridership was eighteen percent higher than it had been in March. The company's marketing director concluded that the eye-catching new paint persuaded more people to ride the ferry.
Which one of the following, if true, most weakens the marketing director's argument?
Show the answer & full explanation
The correct answer is B
The JBDM line
Just because ridership rose after the repainting doesn't mean the paint caused the rise.
The maybes
- MaybeMaybe another way of crossing the bay became unavailable.
- MaybeMaybe warmer spring weather drew more riders.
- MaybeMaybe a seasonal event or festival boosted travel across the bay.
Why B is right
If the only bridge to the mainland closed in mid-April, commuters who normally drove were forced onto the ferry. That's a complete alternative explanation for the ridership jump — one that has nothing to do with paint — so the director's causal story falls apart.
Why the others are wrong
- AVisibility makes the boats noticeable, but noticing a boat isn't evidence that the paint drove ridership — it leaves the causal claim untouched.
- CKiosk paint is a side detail; it neither supports nor undermines the claim about why riders showed up.
- DPassengers liking the color mildly supports the director's story, so it can't weaken it.
- EThe company's repainting history tells you nothing about what caused this particular increase.
Sammy's note
When the conclusion says 'X caused Y,' your first maybe should be a completely different cause.
What's a JBDM line?
Just Because Doesn't Mean (JBDM) is the Burton Method's foundational framework for attacking LSAT arguments: identify the premise, identify the conclusion, then say "just because [premise] doesn't mean [conclusion]" and generate "maybes" — alternative explanations that expose the gap between them. That gap is what weaken, flaw, strengthen, and assumption questions all test, so every explanation on this page starts with the JBDM line. It's a micro-lesson in the system, not just an answer key.
One question a day builds the habit
Answer today's question and start a streak — then see how Sammy teaches the whole system, JBDM included, in a free lesson.