GMAT Book 2: Statistics & Averages

Descriptive Statistics (Statistics and Averages) is a topic from which you could expect 2 to 3 questions in the GMAT quant section. This topic is an important one. The data sufficiency variant in this topic could feature GMAT hard math questions.

Using Wizako's GMAT Prep Material for this topic invest a minimum of 10 hours on the topic.

Concepts Covered in Wizako's GMAT Book

Basics concepts of statistics including averages (arithmetic mean), mode, median, standard deviation, variance, and range are often tested in the GMAT exam. Questions from this topic appear in both the GMAT Problems Solving and in the GMAT Data Sufficiency variant. A good grasp of the fundamentals of these concepts will help you crack questions GMAT statistics and averages with relative ease. Wizako's GMAT Math Lesson Book in this chapter covers the following concepts:

1. Definition of average (arithmetic mean).
2. Weighted average.
3. Standard framework to solve questions involving arithmetic mean and weighted averages.
4. Median and mode.
5. Mean and median of sequences in Arithmetic Progression.
6. What is variance and standard deviation? How to compute standard deviation?
7. What happens to the average and standard deviation of a set of numbers when a constant k is added or subtracted to each term of the set?
8. What happens to the average and standard deviation of a set of numbers when a constant k is multiplied to each term of the set or when each term of the set is divided by a constant k?
9. Arithmetic mean - Geometric mean inequality for positive numbers.
10. 10 illustrative example and 19 solved examples.
11. 12 exercise problems with the answer key and explanatory answers
12. A timed multiple choice test with 40 GMAT level questions in the work book. All questions have been provided explanatory answers.

Here is a typical solved example in Wizako's GMAT Book from this chapter

Sample Question

If x > 14, what is the median of the set consisting of the following numbers: 10, 12, 14, 7, 15, 19, and x?

Explanatory Answer

Arrange the six terms whose values are known in ascending order: 7, 10, 12, 14, 15, and 19.
When x is included, we have seven terms; the median will be the fourth term.
Because x > 14, x will appear to the right of 14 in the sequence.
The 4th term of the sequence, irrespective of where x appears to the right of 14, will be 14.
Therefore, the median is 14.

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