Mastering Statement Analysis for GMAT Data Sufficiency
Data Sufficiency (DS) questions on the GMAT test your ability to determine if you have enough information to solve a problem, not necessarily to solve it yourself. The core skill is analyzing the sufficiency of given statements. This module focuses on effective strategies for dissecting these statements.
Understanding the GMAT Data Sufficiency Question Format
Each DS question presents a problem and two statements. Your task is to determine if either statement alone is sufficient, if both statements together are sufficient, or if neither statement is sufficient. The answer choices are always the same:
Choice | Sufficiency |
---|---|
A | Statement (1) alone is sufficient, but statement (2) alone is not sufficient. |
B | Statement (2) alone is sufficient, but statement (1) alone is not sufficient. |
C | Both statements (1) and (2) together are sufficient, but neither statement alone is sufficient. |
D | Each statement alone is sufficient. |
E | Statements (1) and (2) together are not sufficient. |
Core Strategy: The 'Can I Solve It?' Approach
For each statement, ask yourself: 'Does this statement, on its own, allow me to find a single, unique answer to the question?' If the answer is yes, the statement is sufficient. If there's more than one possible answer, or no answer at all, it's insufficient.
Analyzing Statement (1)
When you look at Statement (1), assume it's true. Ignore Statement (2) completely. Try to solve the problem using only the information in Statement (1). If you can find a unique answer, Statement (1) is sufficient. If not, it's insufficient. This immediately eliminates answer choices B, C, and E.
B, C, and E.
Analyzing Statement (2)
Now, consider Statement (2) on its own, again ignoring Statement (1). Apply the same 'Can I Solve It?' test. If Statement (2) alone gives a unique answer, it's sufficient. If not, it's insufficient. This step helps you distinguish between choices A and D (if Statement 1 was sufficient) or B (if Statement 1 was insufficient).
Analyzing Statements (1) and (2) Together
If neither Statement (1) nor Statement (2) alone is sufficient, you must combine them. Assume both statements are true simultaneously. Can you now find a unique answer to the question? If yes, the answer is C. If even with both statements combined you cannot find a unique answer, the answer is E.
The most common trap in DS is assuming a statement is sufficient because you can perform calculations. Always verify that the calculations lead to a single, unique result.
Special Cases and Advanced Techniques
Be mindful of special cases, especially with number properties. For instance, if a statement implies a variable could be positive or negative, or an integer or a fraction, it's likely insufficient unless the question specifically restricts the domain (e.g., 'positive integers').
Consider a question: 'What is the value of x?' Statement (1): 'x^2 = 4'. This statement is insufficient because x could be 2 or -2. Statement (2): 'x > 0'. This statement is also insufficient as x could be any positive number. Combined: Statement (1) and (2) together imply x^2 = 4 AND x > 0, which uniquely determines x = 2. Therefore, the statements together are sufficient.
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For algebraic questions, try plugging in simple numbers (like 0, 1, -1, 2, -2) to see if you get different results. If you do, the statement is insufficient. For geometry, be aware of diagrams that might not be to scale. Always rely on the given information, not just the visual representation.
Practice Makes Perfect
The key to mastering Data Sufficiency is consistent practice. Work through a variety of problems, focusing on the logic of statement analysis rather than just finding the answer. Pay attention to why insufficient statements fail to provide a unique solution.
Learning Resources
A comprehensive guide covering strategies, common pitfalls, and practice tips for GMAT Data Sufficiency questions.
Explains the core principles and a systematic approach to tackling GMAT Data Sufficiency problems.
Offers a clear, step-by-step strategy for analyzing statements and choosing the correct answer in DS questions.
Provides a foundational understanding of DS questions and a method for evaluating statement sufficiency.
Sample questions from the official GMAT guide, essential for understanding the question style and difficulty.
Breaks down the logic of Data Sufficiency and provides actionable advice for improving performance.
Focuses on understanding the implications of each answer choice (A-E) in Data Sufficiency questions.
A specialized guide on applying DS strategies specifically to number properties questions.
Strategies and examples for solving Data Sufficiency problems involving algebraic concepts.
Tips and techniques for analyzing geometric Data Sufficiency questions, including handling diagrams.