LSAT Necessary and Sufficient Assumptions 5 — Questions and Answers
Question 1: Argument: 'The unemployment rate fell last quarter. When unemployment falls, consumer confidence rises. Therefore, consumer confidence rose last quarter.' A critic challenges: 'Other factors may have suppressed consumer confidence.' The most effective response relies on which assumption?
- Consumer confidence always tracks unemployment perfectly
- No other factor was strong enough to override the effect of falling unemployment on confidence (Correct answer)
- The unemployment statistics were accurately measured
- Consumer confidence is the best economic indicator
Correct answer: No other factor was strong enough to override the effect of falling unemployment on confidence
The argument needs to assume that the relationship between unemployment and confidence wasn't overridden by other forces last quarter.
Question 2: On the LSAT, which question stem signals a Necessary Assumption question?
- 'Which of the following, if assumed, allows the conclusion to be properly drawn?'
- 'The argument assumes which of the following?' (Correct answer)
- 'Which of the following most strengthens the argument?'
- 'The argument is most vulnerable to criticism on the grounds that it…'
Correct answer: 'The argument assumes which of the following?'
'The argument assumes' directly asks for a necessary assumption—something the argument is already implicitly relying on.
Question 3: Which of the following is a sufficient assumption for: 'Maria scored higher than everyone in her class on the entrance exam, so Maria will be admitted to the program'?
- The program values exam performance above all other criteria
- The program admits the student with the highest entrance exam score in any applicant pool (Correct answer)
- Maria prepared extensively for the exam
- The entrance exam is a reliable predictor of success
Correct answer: The program admits the student with the highest entrance exam score in any applicant pool
If the program always admits the top scorer, then Maria's highest score guarantees her admission, making this sufficient.
Question 4: An argument concludes that a policy change caused a drop in crime. A necessary assumption is that:
- Crime statistics are reported by the police
- No other simultaneous change could account for the drop in crime (Correct answer)
- The policy was popular with residents
- Crime was previously very high in the area
Correct answer: No other simultaneous change could account for the drop in crime
A causal argument requires ruling out alternative causes; otherwise the policy change might not be responsible for the drop.
Question 5: A necessary assumption and a sufficient assumption can both be true for the same argument. How do they differ in function?
- The necessary assumption proves the conclusion; the sufficient assumption is optional
- The necessary assumption is required for the argument to work; the sufficient assumption is strong enough to guarantee the conclusion (Correct answer)
- They are functionally identical on the LSAT
- The sufficient assumption must be stated; the necessary assumption is always unstated
Correct answer: The necessary assumption is required for the argument to work; the sufficient assumption is strong enough to guarantee the conclusion
Necessary assumptions are the minimum required; sufficient assumptions provide enough to logically secure the conclusion—both can coexist.
Question 6: Argument: 'This restaurant received a health code violation last year. I will not eat there.' Which necessary assumption does this argument rely on?
- The restaurant has poor food quality
- A past health code violation indicates current or ongoing risk to diners (Correct answer)
- Health inspectors are always accurate
- All restaurants with violations eventually close
Correct answer: A past health code violation indicates current or ongoing risk to diners
The argument moves from a past violation to a current decision, so it must assume the past violation is still relevant to present risk.
Question 7: A law school applicant argues: 'I have a high GPA and LSAT score. Top law schools admit applicants with high GPAs and LSAT scores. Therefore, I will be admitted to a top law school.' A necessary assumption is:
- The applicant has strong recommendation letters
- The applicant's GPA and LSAT are high enough to meet the threshold those schools use (Correct answer)
- Top law schools do not consider personal statements
- The applicant applied to multiple top law schools
Correct answer: The applicant's GPA and LSAT are high enough to meet the threshold those schools use
The argument requires that the applicant's scores meet whatever standard the schools consider 'high'—otherwise the general premise doesn't apply.
LSAT Necessary and Sufficient Assumptions 5
Argument: 'The unemployment rate fell last quarter.
When unemployment falls, consumer confidence rises.
Therefore, consumer confidence rose last quarter.' A critic challenges: 'Other factors may have suppressed consumer confidence.' The most effective response relies on which assumption?