LSAT Strengthen Practice Question: Control Group
An original strengthen question from our free Question of the Day rotation, built around a trap the LSAT reuses constantly: control group. Try it first, then read the explanation — it teaches the move, not just the answer.
Your job:Make the conclusion more believable.
Last spring, the Fernway community garden added compost from its new bins to half of its tomato plots. At harvest, those plots yielded noticeably more tomatoes than they had the previous year. The garden's coordinator concluded that the compost was responsible for the increase.
Which one of the following, if true, most strengthens the coordinator's argument?
Show the answer & full explanation
The correct answer is A
The JBDM line
Just because yields rose after adding compost doesn't mean the compost did it — unless the other maybes get ruled out.
The maybes
- MaybeMaybe the weather was simply better this year.
- MaybeMaybe the whole garden changed its watering routine.
- MaybeMaybe a mild pest season lifted every plot's yield.
Why A is right
The uncomposted plots are a built-in control group. If weather, watering, or pests had driven the increase, those plots should have improved too. They didn't — which isolates the compost as the difference-maker and rules out the biggest alternative explanations at once.
Why the others are wrong
- BHow popular tomatoes are says nothing about what caused this yield increase.
- CMore experienced gardeners on the composted plots is an alternative cause — that would weaken the argument, not strengthen it.
- DWho donated the bins is irrelevant to whether the compost worked.
- EMarket prices have no bearing on how many tomatoes the plots produced.
Sammy's note
The strongest strengthener kills your best maybe.
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.