Logical reasoning question types - Strengthen questions

Learning Outcomes

By the end of this article, you will be able to identify and solve LSAT Logical Reasoning questions that ask you to strengthen arguments. You will understand the structure of such arguments, how to spot assumptions, and common strategies for eliminating incorrect answer choices. You will be able to recognize typical traps and apply targeted methods to select the answer that offers the most support for the argument’s conclusion.

LSAT Syllabus

For LSAT, you are required to understand how strengthen questions fit within logical reasoning. Make sure you revise:

• analytical approaches to arguments and identification of their main point
• finding assumptions and reasoning gaps in given arguments
• recognizing question stems that ask you to support or strengthen the author’s position
• approaches to strengthen question answer choice elimination
• differentiation between strengthen and other question types (e.g. weaken, necessary assumption)

Test Your Knowledge

Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision.

1. Which of the following most strengthens the conclusion of an argument?
   1. Adds unrelated facts
   2. Addresses a key assumption that links premises to conclusion
   3. Directly contradicts the evidence
   4. Repeats information from the argument
2. In strengthen questions, what kind of new information most often appears in the correct answer?
   1. Evidence attacking an alternate cause
   2. Evidence supporting the stated reasoning gap
   3. A general statement about the topic
   4. An irrelevant detail

3. True or false? The correct answer to a strengthen question must prove that the conclusion is 100% true.

4. When faced with two attractive answer choices in a strengthen question, which strategy is best?
   1. Pick the longer answer
   2. Choose the one most directly linked to the conclusion’s reasoning gap
   3. Eliminate both and guess
   4. Pick the answer that repeats premise wording

Introduction

Strengthen questions are a central part of the LSAT Logical Reasoning section. You will need to select the answer that, if accepted as true, makes the argument’s conclusion more likely to be valid. Understanding strengthen questions requires knowledge of argument structure, identification of assumptions, and targeted answer elimination techniques.

For the LSAT, a strengthen question usually consists of:

• a short stimulus containing an argument
• a question stem asking which answer best supports or strengthens the argument
• five answer choices, one of which most increases the argument's logical validity

To solve these questions, you must find the “gap” between premise and conclusion—the missing link the author assumes to reach their conclusion.

Key Term: strengthen question
A question type that asks for the answer choice which, if true, provides additional support to the argument’s reasoning or conclusion.

Argument Structure in Strengthen Questions

LSAT arguments typically have:

• premises (stated evidence or reasons)
• a conclusion (the main point to be established)
• an unstated assumption (linking the evidence to the conclusion)

Key Term: assumption
An unstated idea or claim the author relies upon; in strengthen questions, answers often support or supply these assumptions.

Recognizing Strengthen Questions

You can spot these by typical question stems such as:

• Which one of the following, if true, most strengthens the argument?
• Which one of the following, if true, provides the strongest support for the author’s conclusion?
• Which one of the following, if true, most helps to justify the reasoning above?

Typical Strengthen Answer Choices

Correct answers in strengthen questions:

• directly address a logical gap or assumption
• provide extra evidence supporting the link between premises and conclusion
• rule out an alternative explanation
• give data or principles that confirm the author’s logic

Incorrect answers usually:

• repeat premises
• are irrelevant to the argument’s core reasoning
• weaken or contradict the argument
• are out of scope or deal with side issues

Worked Example 1.1

Stimulus: "Researchers observed that people who take vitamin D supplements have fewer colds. Therefore, taking vitamin D reduces the risk of getting a cold."

Which answer choice most strengthens the argument?

A) People who take vitamin D also tend to eat more fruits and vegetables.
B) People who took vitamin D had similar cold rates as people who did not.
C) Vitamin D has been shown in laboratory studies to boost immune response to cold viruses.
D) Some participants forgot to record all their illnesses.
E) Most vitamin D users live in warmer climates.

Answer:
C. Laboratory evidence showing vitamin D actively improves immunity directly supports the claim that vitamin D reduces colds. The other options either introduce confounds, are irrelevant, or weaken the claim.

Worked Example 1.2

Stimulus: "City X’s new bike lanes will reduce traffic accidents. Recently, cities that installed similar lanes saw accident rates fall by 25%."

Which of the following most strengthens the argument?

A) Bike accidents in City X have always been low.
B) The new bike lanes are painted green for improved visibility.
C) In cities with similar new lanes, traffic patterns resemble those in City X.
D) Building bike lanes cost less in City X than in other places.
E) Most car accidents do not involve bicycles.

Answer:
C. Showing that the cities cited in the evidence are similar in traffic patterns to City X makes the analogy valid, providing strong support for the argument.

Common Strengthen Question Strategies

• Identify the premises and conclusion.
• Look for an assumption or reasoning gap.
• Predict what type of support is needed.
• Use process of elimination on answer choices:
  • Remove answers that are unrelated, irrelevant, or too weak.
  • Be cautious of answers that use identical wording as the argument but do not add new support.
• Confirm the correct answer supplies a key link between premise and conclusion or eliminates a major alternative explanation.

Revision Tip

When stuck between two choices, choose the one that most clearly addresses how the author moves from the evidence to the conclusion—even if it seems less “obvious” or uses unfamiliar wording.

Exam Warning

Do not confuse "strengthen" with "prove." The correct answer does not need to make the conclusion 100% certain—just more likely to be correct.

Key Term: premise
A statement in an argument given as a reason or evidence to support the conclusion. Common premise indicators include "because," "since," "for," and "after all."

Key Term: conclusion
The main claim of the argument, what the author wants you to accept based on the premises.

Question Types Commonly Confused with Strengthen

• Weaken questions: Ask for an answer that undermines the argument
• Necessary assumption questions: Ask for a statement that must be true for the conclusion to be valid
• Sufficient assumption questions: Ask for a claim that guarantees the conclusion

Worked Example 1.3

Stimulus: "Car dealership advertisements make people more likely to buy new cars. After a major advertising campaign, sales rose 20%."

Which, if true, most strengthens the argument?

A) The increase in car sales corresponded with a national drop in used car prices.
B) Other dealerships in the same city did not advertise and did not see a sales increase.
C) The month after the campaign, snowfall was unusually low.
D) Customers who bought cars often cited the advertisements as an important reason.
E) City car shows took place during the campaign month.

Answer:
D. Direct evidence that customers were influenced by the advertisements is the best support. (B) is plausible but less direct; (A), (C), and (E) are potential confounding factors or irrelevant.

Key Point Checklist

This article has covered the following key knowledge points:

• Strengthen questions require you to find evidence that makes the argument more convincing.
• The correct answer will address a reasoning gap or an assumption—not merely restate a premise.
• Common wrong answers are irrelevant, repeat the stimulus, or actually weaken the argument.
• Strengthen answers do not need to give absolute proof, only make the conclusion more likely.
• Elimination strategies are essential: target answer choices that directly link evidence and conclusion.
• Recognizing strengthen question stems and answer choice patterns is essential for avoiding traps.

Key Terms and Concepts

• strengthen question
• assumption
• premise
• conclusion