Weakened Questions in Logical Reasoning

Weakened Questions in Logical Reasoning

Overview

  • Weakened questions are a common question type in the logical reasoning section, comprising about 9% of all questions.
  • Skills used in weakened questions are also beneficial for strengthened and paradox questions.

Identifying Weakened Questions

  • Identified by specific language in the question stem.
    • Examples:
      • "Which one of the following, if true, most seriously weakens the argument above?"
      • "Which one of the following, if true, casts the most doubt on the argument above?"
      • "Which one of the following, if true, most seriously undermines the argument above?"
  • Keywords: weakens, undermines, casts doubt on.
  • The word "most" is important because the answer needs to have the strongest impact.

Process for Approaching Weakened Questions

  • The process is the same as for other question types in the assumption family (assumption, necessary assumption, flaw, strength questions).
  • Steps:
    1. Find the Conclusion: Identify the main conclusion of the argument.
    2. Identify the Evidence: Determine the evidence provided to support the conclusion.
    3. Evaluate the Argument:
      • Concede the evidence (assume it's true).
      • Challenge the conclusion (determine if the conclusion has to be true, even if the evidence is).
      • Look for the space or gap between the evidence and the conclusion.
    4. Anticipate the Answer: Based on the gap, anticipate what the correct answer choice would look like.
    5. Evaluate Answer Choices: Pair anticipation with an answer choice or use trap answer patterns to eliminate wrong answers.

Reasoning Structures: Comparisons

  • Comparisons are common in logical reasoning arguments.
  • Types of comparisons:
    • Comparing two different things at a point in time (e.g., population of city A vs. city B).
    • Comparing a thing at two different points in time (e.g., population of city A ten years ago vs. today).
  • Identifying comparisons helps to find the gap in the argument.
Example: Airlines and Leisure Travelers
  • Argument: Airlines are overly concerned about the comfort of passengers flying business class and should instead focus on the comfort of leisure travelers because leisure travelers book 80% of all airline tickets.
  • Analysis:
    • Conclusion: Airlines should focus on the comfort of leisure travelers.
    • Evidence: Leisure travelers book 80% of airline tickets.
    • Opposing Argument: Airlines are increasing elbow room in business class because surveys show business travelers value additional space more than meals.
  • Evaluation:
    • The argument assumes focusing on leisure travelers makes financial sense for airlines.
    • It's possible that business class travelers, though fewer, generate more revenue due to higher ticket prices.
  • Weakening the Argument:
    • The argument can be undermined by showing a financial incentive to focus on business class travelers.
  • Answer Choice Analysis:
    • (A) (Incorrect): "Business travelers often make travel decisions based on whether they feel a given airline values their business." - Too weak because "often" doesn't mean it's significant enough, and it doesn't exclude the possibility that the minimum threshold is already met and additional efforts should go to leisure travelers anyway.
    • (B) (Incorrect): "Some airlines have indicated that they will undertake alterations in seating space throughout the entire passenger area of their planes in the near future." - Too weak because it doesn't specify if the alterations are in favor of business or leisure travelers.
    • (C) (Incorrect): "Sleeping in comfort during long flights is not the primary concern of leisure travelers." - Too weak because sleeping in comfort is one aspect of comfort.
    • (D) (Correct): "A far greater proportion of an airline's revenues is derived from business travelers than from leisure travelers." - Directly compares the revenue significance of business travelers and leisure travelers, undermining the argument.
    • (E) (Incorrect): "Most leisure travelers buy airline tickets only when fares are discounted." - Too weak; it could go either way (they don't care about comfort, or they can't afford comfortable tickets).

Reasoning Structures: Causation

  • Causation is a strong relationship (A causes B) and hard to prove.
  • Attacking causal conclusions is a good strategy for weakened questions.
  • Tactics to weaken causal arguments:
    • Provide an alternative cause.
    • Provide an example of the presumed cause without the presumed effect.
    • Provide an example of the effect without the cause.
Example: Irradiated Food
  • Argument: There are good reasons to avoid irradiated food (conclusion). Irradiation exposes foods to radioactive substances, reduces vitamin content, leaves harmful chemical residues, and spawns unique radiolytic products that cause serious health problems (evidence).
  • Analysis:
    • Conclusion: Avoid irradiated foods.
    • Evidence: Irradiated foods are exposed to radioactive substances which produce gamma rays. Irradiation reduces vitamin content in foods. Irradiation spawns radiolytic products that produce cancer.
    • The evidence presents a causal relationship.
  • Weakening the Argument:
    • Look for alternative causes, irradiated foods that aren't bad, or bad foods that aren't irradiated.
  • Answer Choice Analysis:
    • (A) (Incorrect): "Unique radiolytic products have seldom been found in any irradiated food." - Cause (irradiated food) without effect (radiolytic products). Weakens the argument.
    • (B) (Correct): "Cancer and other serious health problems have many causes that are unrelated to radioactive substances and gamma rays." - Brings up other things that cause cancer, but it doesn't rule out the fact that radiation causes cancer.
    • (C) (Incorrect): "A study showed that irradiation leaves the vitamin content of virtually all fruits and vegetables unchanged." - Stronger and broader to include all fruits and vegetables, undermining the second point in the argument.
    • (D) (Incorrect): "The amount of harmful chemicals found in irradiated foods is less than the amount that occurs naturally in most kinds of foods." - Saying that these harmful chemicals are really not that many of them to make significant.
    • (E) (Incorrect): "A study showed that the cancer rate is no higher among people who eat irradiated food than among those who do not." - Cause (irradiated food) without effect (higher cancer rate). Weakens the argument.

Trap Answer Patterns

  • Out of Scope: New information that isn't related.
  • Opposite Logic: Strengthens the argument instead of weakening it.
  • Irrelevant Relationships: Builds a comparison with no impact, or links two random terms.
  • Term Shifts: Tweaks terms to be too weak.
  • Degree: Answers that are too weak to have a significant impact.

Strategies for Eliminating Answer Choices

  1. Scope: Eliminate out-of-scope answers first.
  2. Logic: Then, eliminate answers with incorrect logic or irrelevant relationships.
  3. Degree: Finally, consider the strength of the remaining answers, preferring stronger (more impactful) answers.