CHAPTER 23

Statistics on the GMAT

Learning Objectives

After studying this chapter, you will be able to: 

• Describe the types of statistics routinely tested on the GMAT
• Identify questions that involve statistics concepts
• Apply the Kaplan Methods for Problem Solving and Data Sufficiency to a variety of different question types that deal with statistics

Below is a typical Data Sufficiency question dealing with probability, one of the categories of statistics that we will discuss in this chapter. In this chapter, we’ll look at how to apply the Kaplan Method to this question, discuss the probability rules being tested, and go over the basic principles and strategies that you want to keep in mind on every Quantitative question involving statistics.

1. Tracy has 3 bags of marbles, each bag containing at least 1 blue marble, at least 1 red marble, and no marbles of another color. If Tracy selects 1 marble at random from each bag, what is the probability that all 3 marbles that she selects will be red?
   1. There is a total of 5 red marbles and 5 blue marbles in the 3 bags.
   2. The ratios of red to blue marbles in the 3 bags are 2:1, 1:1, and 1:2.

Before you move on, take a minute to think about what you see in this question and answer some questions about how you think it works:

• What does probability measure?
• How can ratios help you calculate probability on this question?
• What Kaplan strategy can you use to solve this question?
• What GMAT Core Competencies are most essential to success on this question?