Logical Reasoning · Evaluate

PrepTest 153 · Section 2 · Question 3

Phase 1 (your first ~400 questions): read the guidance, then answer. No clock.

Step 1 · Pre-Question Guidance · read this first

Question type

Evaluate

The one idea it tests

A comparison argument that gives a number for only one side is incomplete: you need the matching number for the other side.

The basic logic

The evidence tells you how often one group gets checked. The conclusion says pick the other group. Use the Seesaw Test: the useful question is the one whose answer could tip the argument either way, usually the missing number for the side being recommended.

Tiny words that decide it

“only”
“so”
“should”

Playground logic

Marcus gives one number (Sunny Park slides rarely get checked) and jumps to a top bun (play only at Maple Park). The secret sauce is that Maple Park slides get checked more. Ask how often Maple Park slides are checked, and the seesaw tips.

Step 2 · The kid story

Marcus Picks a Park

Marcus stands on the bench like a detective giving a speech. "Hear this! Only one out of every twenty slides at Sunny Park gets a safety check. So if you want a safer slide, play only at Maple Park!" Owen nods. Nadia almost nods. Lulu raises her clipboard. "Wait. How many Maple Park slides get a safety check?" Marcus freezes. "I... did not look." Priya explains. "If Maple Park checks every slide, your plan looks great. If Maple Park checks none, your plan is backwards. You only told us half the story." Marcus climbs down. "Investigation reopened."

Step 3 · Try the model question

Marcus: Only one in twenty slides at Sunny Park gets a safety check. So kids who want a safer slide should play only at Maple Park.

Knowing the answer to which question would be most useful for judging Marcus's reasoning?

Step 4 · The courtroom tale

The Case of the Two Ferries

Ms. Lane sued a travel guide that said: "Only a few Red Line ferries get engine inspections, so travelers should take only Green Line ferries." The guide's lawyer, Mr. Whitfield, beamed. "Your Honor, the number is correct." Judge Kim peered over her glasses. "Correct for Red Line. And how many Green Line ferries get inspected?" Silence. Mr. Whitfield checked his notes, then his pockets, then the ceiling. "That figure is not in our file, Your Honor." The judge sighed. "Then the advice has only one side of the scale. If Green Line inspects even fewer, the advice sends people the wrong way." Mr. Whitfield tugged his suspenders. "We will go find that number."

Step 5 · Work the real question

Open PrepTest 153, Section 2, Question 3 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Identify what the evidence measures and for which group. Then see which group the conclusion recommends. Ask: what fact about the recommended group would make the advice right or wrong? Run the Seesaw Test on each choice: imagine one answer, then the opposite answer. Keep only the question whose answers would push the argument in opposite directions. Discard questions whose answers would leave the comparison untouched.