Logical Reasoning · Flaw

PrepTest 129 · Section 2 · Question 26

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

Step 1 · Pre-Question Guidance · read this first

Question type

Flaw

The one idea it tests

Evidence comes from a source with a reason to be biased, and the argument trusts it anyway.

The basic logic

Find what the conclusion rests on, then ask who produced that evidence. If those people had a grudge created by the very person they judge, the evidence is a Weird Sample: not a fair picture of what everyone thought.

Tiny words that decide it

“conclude”
“widely”
“because of”

Playground logic

Marcus says the snack manager is disliked by everyone because the Candy Club filled the complaint box. But the Candy Club lost its candy because of her, so their notes are a Weird Sample: a group with a reason to grumble, not a fair read of the whole school.

Step 2 · The kid story

The Complaint Box Caper

The new snack bar manager, Mrs. Pell, believes in fruit and only fruit. She stopped buying candy for the snack bar. Then the suggestion box overflowed with grumpy notes about her. Marcus put on his detective hat. 'Clear case. Everyone in school dislikes Mrs. Pell. Look at all these complaints!' Priya pulled out a few notes and read the signatures. 'Candy Club. Candy Club. Candy Club president.' Nadia raised an eyebrow. 'The Candy Club just lost all its candy because of her. Of course they're grumpy.' Owen added, 'Half the kids I know love the apple slices.' Marcus slowly lowered his hat. 'So the notes come from the people most likely to be mad.' Biscuit, who also missed the candy, said nothing.

Step 3 · Try the model question

Mrs. Pell, who strongly prefers fruit, stopped stocking candy at the snack bar. Also, Mrs. Pell is disliked by most students, as shown by the many complaint notes about her in the suggestion box from members of the Candy Club.

Which choice best describes a weakness in this reasoning?

Step 4 · The courtroom tale

The Parking Lot Petition

The prosecutor held up a thick stack of letters. 'Your Honor, the mall manager is hated by the whole town. Look at all these angry letters!' Mr. Whitfield squinted at them. 'May I ask who wrote them?' The prosecutor shuffled. 'Well, the food truck owners.' 'The same food truck owners,' said Mr. Whitfield, 'whom my client banned from the parking lot last spring?' Murmurs filled the room. 'Of course they are angry. That tells us how the food truck owners feel, not how the whole town feels.' The judge nodded. 'Letters from people with a grudge are a lopsided sample, counselor.'

Step 5 · Work the real question

Open PrepTest 129, Section 2, Question 26 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Find the conclusion about how a wide group feels and the evidence offered for it. Then ask who made that evidence, and whether something else in the argument gave them a reason to lean one way. Predict the flaw in your own words: a biased source treated as fair. Pick the choice that names that problem, and skip ones about side details or claims the argument never makes.