Simplify GMAT Critical Reasoning: The "Because Y; Therefore Z" Method

Mastering GMAT Critical Reasoning can be challenging, but there’s a strategy that simplifies the process — the "Because Y; Therefore Z" method. This approach helps break down arguments into clear, manageable parts, making it easier to analyze and answer questions. In this post, we’ll demonstrate how to apply this method using a high school example and guide you through the thought process step by step.

What Is the "Because Y; Therefore Z" Method? The "Because Y; Therefore Z" method helps you break down an argument by focusing on the premise (Y) and the conclusion (Z). This method is particularly useful for assumption questions, where the argument depends on unstated premises to hold up.

• Y (Premise): The reason or evidence that supports the argument.
• Z (Conclusion): The claim or result derived from the premise.

By understanding the connection between Y and Z, you can identify flaws, assumptions, or weaknesses in the reasoning, which helps you zero in on the right answer.

High School Example:

Let’s look at a real-life example from a high school scenario:

“In 2001, a local high school implemented a new program designed to reduce the incidence of teenage pregnancy. The program, however, failed to produce the desired result. If the program had been successful, the dropout rate for female students would not have increased substantially in 2001.”

• Z (Conclusion): The program failed to reduce teenage pregnancy because the dropout rate for female students increased substantially.
• Y (Premise): If the program had been successful, the dropout rate would not have increased.

The argument assumes a direct link between teenage pregnancy and female student dropouts, which the passage uses to claim that the program was ineffective. This sets up the structure for the assumption question, where the argument depends on certain unstated premises.

How to Break Down the Example:

1. Categorize the Question: This is an assumption question, where you need to identify an unstated assumption that the argument relies on. The question stem doesn’t ask for a conclusion or to strengthen/weaken the argument, but rather which assumption is critical to the reasoning.
2. Deconstruct the Argument: Let’s isolate the conclusion: “The program to reduce teenage pregnancy was a failure because the dropout rate for female students increased in 2001.” Why does the author conclude that the program was a failure? The premise is that if the program had been effective in reducing teenage pregnancies, the dropout rate should have gone down, not up. The author’s reasoning here is that teenage pregnancy is a major factor in why female students drop out. However, this is not explicitly stated — it’s an assumption we need to identify.
3. Attack the Argument: Now that we understand the structure of the argument, let’s anticipate alternative explanations. What else could have caused the increase in dropouts, other than the program’s failure to reduce teenage pregnancy? Perhaps the dropout rate rose due to economic factors, or maybe there was an increase in student transfers to other schools. The argument hinges on the assumption that teenage pregnancy is the primary cause of female student dropouts.
4. Evaluate the Answer Choices:

Conclusion: The "Because Y; Therefore Z" method helps you systematically analyze GMAT Critical Reasoning questions by breaking down the argument into premises and conclusions. In this high school example, the argument relied on the assumption that teenage pregnancy was the main reason for the increase in dropouts. By identifying this assumption, you can confidently answer the question. For more GMAT tips and strategies, visit Merchant GMAT & Admissions to get expert guidance on your journey to success.