Logical Reasoning: How Additional Evidence Affects an Argument
LSAC's evidence-effect family drawn as a balance: strengthen, weaken, evaluate, justify and the EXCEPT stems that invert all of them.
7 topics · 27 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
Strengthen Questions
- How it worksHow does dropping a weight into the conclusion's pan change how likely that conclusion becomes?
- Worked exampleFind what most strengthens 'The bakery will profit, since its rent is low and its pastries sell out'.
- Common mistakeWhy doesn't the loudest, most sweeping answer strengthen the most?
- Going furtherWhat changes when a stem asks which answer most helps justify instead of merely strengthens?
Your turneasy1 of 3
Owner: our rent is 25 hundred a month, well below the average on this street, and our pastries sell out by 13 o'clock on most days. The bakery will turn a profit this year. Which one of the following, if true, most strengthens the owner's conclusion?Weaken Questions
- How it worksHow does a weakener go after the join between evidence and conclusion instead of the evidence?
- Worked exampleFind what most weakens 'Our ad worked, since sales rose the week after it aired'.
- Going furtherWhat happens to a weakener when the conclusion is a recommendation rather than a claim of fact?
- Common mistakeWhy isn't the credited weakener usually the answer that flatly calls a premise wrong?
Your turneasy1 of 3
Marketing lead: our radio advertisement aired on the 18th, and sales the following week were 22 percent above the week before. The advertisement worked. Which one of the following, if true, most weakens the lead's conclusion?Attacking the Link, Not the Premises
- How it worksHow does the gap between the evidence block and the conclusion block become the only legal target?
- Worked exampleWalk me through attacking 'Lakeview has the best schools, since its students score highest'.
- Common mistakeWhy isn't an answer that simply denies a stated fact ever the credited weakener?
- Going furtherWhat changes when the thing you want to attack is itself an intermediate conclusion?
Your turnmedium1 of 3
School board: pupils at Lakeview scored 23 points above the district average on this year's assessment, so Lakeview has the best schools in the district. Which one of the following, if true, most weakens the board's argument?Evaluate the Argument
- How it worksHow does the variable test check whether answering a question either way actually moves the argument?
- Worked exampleWalk me through evaluating 'The diet works, since everyone in our office who tried it lost weight'.
- Worked exampleFind which question best tests 'The bridge is safe, because no accident has ever happened on it'.
- Common mistakeWhy isn't a relevant-sounding question good enough when both possible answers leave the argument alone?
Your turnmedium1 of 3
Manager: all 14 people in this office who tried the diet lost weight, so the diet works. Which one of the following would be most useful to know in evaluating the manager's argument?Justify the Conclusion
- How it worksHow does a justifying answer bolt the term found only in the evidence to the one found only in the conclusion?
- Common mistakeWhy isn't an answer that merely helps enough when the stem demands the conclusion follow?
- Worked exampleFind what justifies 'Rosa will be hired, since she has ten years of courtroom experience'.
- Going furtherWhat changes when several answers each close the gap and you must take the narrowest one?
Your turnmedium1 of 3
Partner: Rosa has 13 years of courtroom experience, so Rosa will be hired for the trial post. Which one of the following, if assumed, allows the partner's conclusion to be properly drawn?Strengthen-EXCEPT and Weaken-EXCEPT
- How it worksHow does sorting every choice into helps, hurts, or does nothing crack an EXCEPT stem fast?
- Worked exampleWalk me through a Weaken-EXCEPT on 'The vaccine works, since flu cases fell in vaccinated towns'.
- Common mistakeWhy isn't the credited answer to a Strengthen-EXCEPT question always one that weakens?
Your turnmedium1 of 3
Health board: flu cases fell 36 percent in the 13 towns where the vaccine was offered free, so the vaccine works. Each of the following, if true, weakens the board's argument EXCEPT:Answers That Merely Restate a Premise
- How it worksHow does a restated premise land on the balance as a weight that was already sitting there?
- Worked exampleWalk me through why 'sales rose after the ad' cannot strengthen an argument whose evidence is that sales rose.
- Common mistakeWhy doesn't a smooth paraphrase of the conclusion count as evidence for that conclusion?
- Going furtherWhat changes when an answer restates a premise but tacks one genuinely new fact onto the end?
Your turneasy1 of 3
Argument: sales rose 23 percent in the 7 weeks after the advertisement aired, so the advertisement raised sales. Which one of the following answers adds no support to that argument?AP®, SAT® and PSAT/NMSQT® are trademarks registered by the College Board (PSAT/NMSQT® jointly with the National Merit Scholarship Corporation). ACT® is a registered trademark of ACT Education Corp. GRE® is a registered trademark of ETS. LSAT® is a registered trademark of the Law School Admission Council. MCAT® is a registered trademark of the Association of American Medical Colleges. ISEE® and SSAT® are registered trademarks of their owners. None of these organizations is affiliated with, or endorses, Jentoo.