Logical Reasoning · Necessary Assumption

PrepTest 151 · Section 2 · Question 5

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

Step 1 · Pre-Question Guidance · read this first

Question type

Necessary Assumption

The one idea it tests

A chain of helpers leads to a quality, and the conclusion talks about a different payoff; the bridge from the quality to the payoff is assumed.

The basic logic

Follow the links: X does this, which does that, which makes it Y. The conclusion says X is more effective. The missing plank: things that are Y usually work better.

Tiny words that decide it

“generally”
“more”
“this makes”

Playground logic

Priya's top bun: story-style reports get better grades. Her patty ends at 'fun to listen to.' The secret sauce is that fun-to-hear reports generally earn better grades. Pull that plank and the argument falls.

Step 2 · The kid story

The Story Report

Priya had a theory. "Story-style book reports generally get higher grades than fact-list reports." Marcus scoffed. "Prove it." "A story report ties all the facts into one adventure, with a beginning, middle and end. That makes it fun to listen to." Lulu tapped her clipboard. "Wait. You jumped. You said fun to listen to. Then you said higher grades. Who said fun means better grades?" Priya smiled. "Good catch. I'm counting on that. If fun reports don't generally score better, my whole idea falls flat." Kevin raised his hand. "My report on the T. rex was very fun. I got a C." Everyone stared. "See?" said Lulu. "That's the plank."

Step 3 · Try the model question

Story-style book reports generally earn higher grades than fact-list reports. A story report weaves the facts into one adventure with a beginning, middle and end. This makes the report fun to listen to.

The argument depends on which assumption?

Step 4 · The courtroom tale

The Glitter Poster Trial

In a fictional town contest, a sign maker claimed glitter posters generally win more votes. "Glitter catches the light," said Mr. Whitfield, "which draws the eye, which makes the poster eye-catching." The opposing lawyer stood. "Your Honor, he stops at eye-catching. The contest is decided by votes. He needs eye-catching posters to generally win more votes. If they don't, his case is glitter and nothing else." Mr. Whitfield paused. "Fine. I assume eye-catching posters win more votes." "Then say so," said the judge, "because without it, your argument sparkles but doesn't stand."

Step 5 · Work the real question

Open PrepTest 151, Section 2, Question 5 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Find the conclusion and the last link of the premise chain. Notice that the conclusion's key term does not appear in the premises. The required assumption connects the last link to that term. Use the Pull the Plank test on each choice: negate it, and if the argument falls apart, that is the answer. Watch for choices about memory, context, or audience interest that are side issues.