Logical Reasoning · Weaken
PrepTest 131 · Section 3 · Question 13
Phase 1 (your first ~400 questions): read the guidance, then answer. No clock.
Step 1 · Pre-Question Guidance · read this first
- “percentage”
- “of those”
- “thus”
Playground logic
Marcus's patty: among kids who fell at recess, few dome climbers got scraped, but lots of slide kids got scraped. His top bun: you are less likely to get scraped on the dome. The pin that pops it: dome kids fall far more often in the first place.
Step 2 · The kid story
The Dome of Safety?
Nurse Kim kept a list of every kid who fell at recess this year. Marcus studied it like a detective. "Look! Of the kids who fell off the climbing dome, hardly any got scraped. Of the kids who fell off the little slide, tons got scraped. Case closed: you're less likely to get scraped if you play on the dome." Priya peeked at the list. "Marcus, how many kids fell off the dome?" He counted. "Um. Two hundred." "And the slide?" "Six." Lulu wrote on her clipboard: Few scrapes per fall, but SO many falls. Priya sipped her juice box. "If dome kids fall all the time, they might still get scraped more often overall." Marcus slowly put the list down.
Step 3 · Try the model question
Among all kids who fell at recess this year, a small share of dome climbers got scraped, while a large share of slide players got scraped. So a kid is less likely to get scraped by playing on the dome rather than the slide.
Suppose each choice is true. Which most weakens Marcus's argument?
Step 4 · The courtroom tale
The Ladder Lawsuit
A ladder company boasted: "Among workers who slipped on a ladder, few of ours were hurt, while many using the rival brand were hurt. So our ladder keeps you safer!" Mr. Whitfield, for the rival, rose slowly. "Your Honor, look at how often each ladder sees a slip." He held up a chart. "Workers on their ladder slip ten times as often as workers on ours." Judge Okafor studied it. "So even with fewer injuries per slip, their ladder may produce more injuries overall." Mr. Whitfield nodded. "Exactly. They only counted the people who had already slipped." The ladder company's lawyer looked down, very carefully.
Step 5 · Work the real question
Open PrepTest 131, Section 3, Question 13 in your official copy from LSAC (for example in LawHub) and read it there.
Your answer
How to apply it
Check who is in the study: only people who already had the bad event. Then check the conclusion: it speaks about overall likelihood. The gap is how often each group has the event at all. Look for the choice showing the group that looks safer actually has the event far more often. Skip choices about conditions shared by everyone or about overall low rates that hit both groups equally.