GMAT Review: Common Fallacies (Causation vs Correlation, Overgeneralization, False Dilemma)

GMAT – Common Fallacies (Causation vs Correlation, Overgeneralization, False Dilemma)

GMAT Study Guide – Common Fallacies (Causation vs. Correlation, Over‑generalization, False Dilemma)

What This Is

A fallacy is a flaw in reasoning that makes an argument invalid or unsound. On the GMAT, fallacies appear most often in Critical Reasoning (CR) and Reading‑Comprehension (RC) passages. Recognizing whether an author is mistaking correlation for causation, over‑generalizing, or presenting a false dilemma lets you spot the “right‑answer‑trap” and choose the answer that truly weakens or strengthens the argument.

Typical GMAT CR stem: “The city council argues that because crime rates dropped after the new lighting program was installed, the program caused the decline. Which of the following, if true, most seriously weakens the council’s conclusion?”

Key Terms & Rules

• Correlation vs. Causation – The error of assuming that because two variables move together, one must cause the other.
• Over‑generalization – Drawing a broad conclusion from a limited set of evidence (e.g., “All startups fail” after hearing about three failures).
• False Dilemma (Either/Or) – Presenting only two alternatives when a third (or more) viable option exists.
• Strengthen / Weaken – In CR, the answer must increase or decrease the logical force of the argument; never merely add unrelated facts.
• Assumption – An unstated premise that the argument must be true for the conclusion to hold; often the target of “must be true” questions.
• Inference – A conclusion drawn from the given data; CR “must be true” questions often test whether an inference is justified.
• “Because of” vs. “With” – In the stem, “because of” signals a causal claim; “with” signals a correlation.
• Answer‑Choice Patterns – Weakening answers for causation fallacies usually introduce an alternative cause; for over‑generalization they provide a counter‑example; for false dilemmas they add a third option.
• Data Sufficiency Parallel – Though fallacies are verbal, the same “don’t assume” mindset applies: never accept a statement as sufficient unless the information is explicitly given.
• “All‑or‑Nothing” Language – Words like “always,” “never,” “only,” or “must” often cue a false dilemma or over‑generalization.

Step‑by‑Step / Process Flow

1. Read the stem carefully – Identify the conclusion and any causal language (“because,” “as a result of”).
2. Spot the fallacy type – Look for correlation language, sweeping statements, or “either/or” phrasing.
3. Translate the argument into a simple logical skeleton (e.g., A → B for causation; All X are Y for over‑generalization).
4. Ask “What would make this skeleton invalid?” – For causation, think of alternative causes; for over‑generalization, think of exceptions; for false dilemma, think of additional choices.
5. Scan answer choices for the pattern identified in step 4 – Choose the one that directly attacks the logical link without adding unrelated facts.

Common Mistakes

• Mistake: Selecting an answer that adds new information instead of undermining the logical link.
  Correction: The correct answer must break the assumed relationship, not simply provide extra data.

• Mistake: Confusing correlation with causation and choosing a “strengthen” answer that merely shows the two variables move together.
  Correction: For a causation fallacy, a weakening answer must present an alternative cause or show the correlation could be coincidental.

• Mistake: Over‑looking a hidden third option in a false‑dilemma question and picking the “either/or” answer.
  Correction: Look for answer choices that introduce a third viable alternative; that is the classic weakening move.

• Mistake: Assuming a counter‑example automatically weakens an over‑generalization without checking relevance.
  Correction: Verify that the counter‑example directly contradicts the sweeping claim; irrelevant examples are distractors.

• Mistake: Treating “must be true” questions as “strengthen” questions.
  Correction: Identify the assumption first; the correct answer will be the statement that, if true, makes the argument logically necessary.

Exam Insights

1. GMAT loves “because of” – Any stem that uses “because of” is a red flag for a causation fallacy; the test will almost always expect an alternative cause answer.
2. All‑or‑nothing wording – Words like “only,” “always,” or “never” signal a false dilemma or over‑generalization; the correct answer will introduce a middle ground or exception.
3. The “single‑example” trap – A single data point is rarely enough to support a broad claim; the GMAT frequently offers a single‑example answer that looks plausible but does not actually refute the generalization.
4. Answer‑choice “but” – In weakening questions, the correct answer often contains the word “but,” indicating it contradicts the premise while preserving the rest of the argument.

Quick Check Questions

1. Critical Reasoning – Causation
   Stem: “Since the company introduced a flexible‑hours policy, employee turnover dropped by 15 %. Management concludes the policy caused the drop.”
   Which of the following, if true, most seriously weakens the conclusion?
2. A) Turnover had been falling 5 % each year for the past three years.
3. B) A rival firm closed its regional office, causing many employees to relocate.
4. C) The flexible‑hours policy was adopted only in the sales department.
5. D) Employee satisfaction scores rose by 8 % after the policy.
6. E) The company hired a new HR director at the same time.

Answer: B – It provides an alternative cause (the rival’s closure) for the turnover decline.

1. Critical Reasoning – Over‑generalization
   Stem: “All of the recent graduates who took the new software course got jobs within three months; therefore, the course guarantees employment.”
   Which answer most weakens the argument?
2. A) Some graduates who did not take the course also found jobs quickly.
3. B) One graduate who completed the course is still unemployed after six months.
4. C) The course costs more than the average certification.
5. D) The hiring market for software engineers is expanding.
6. E) The course includes a résumé‑building workshop.

Answer: B – A single counter‑example disproves the “all” claim.

1. Critical Reasoning – False Dilemma
   Stem: “The committee must either increase tuition or cut faculty salaries to balance the budget.”
   Which answer most weakens the dilemma?
2. A) Raising tuition would likely cause enrollment to drop.
3. B) The university could also reduce administrative expenses.
4. C) Faculty salaries are already below market rates.
5. D) Tuition hikes are unpopular with students.
6. E) Cutting salaries would lower morale.

Answer: B – Introduces a third viable option (cutting admin costs).

Last‑Minute Cram Sheet (10 One‑Liners)

1. ⚠️ Causation fallacy → look for “because of,” “as a result of”; weakening answer = alternative cause.
2. Over‑generalization → watch for “all,” “always,” “never”; weakening answer = single counter‑example.
3. False dilemma → spot “either/or,” “must choose”; weakening answer = third option.
4. Assumption = unstated premise; “must be true” questions target it.
5. Strengthen = add support to the logical link; Weaken = break the link.
6. In CR, the most powerful answer often contains the word “but.”
7. Correlation language (“with,” “alongside”) signals no causal claim – treat as neutral unless “because of” appears.
8. Answer‑choice pattern: For causation, the correct answer usually starts with “If” and introduces a new factor.
9. Data Sufficiency parallel: Never assume anything not explicitly given; the same discipline applies to verbal fallacy questions.
10. Time‑saving tip: Convert the argument to a simple schematic (e.g., A → B, All X are Y, A or B) → spot the missing link → scan for answer that breaks that link.

Good luck—mastering these fallacies will turn many “trick” CR questions into quick wins!