# Welcome!

A good day to you! In the 18th and 19th centuries, instead of saying “Welcome!” people would say, “A good day to you!” Why should this be important for you in a mathematics lesson? In this module, our friends Andrew and Khalid are discovering mathematics in American history!

In this module, you will:

• Explore statistical methods to describe the spread of data.
• Work with two new concepts, mean absolute deviation and standard deviation.
• Learn the difference between the two deviations and when one is more appropriate to use.

Some of the concepts you will learn are used by historians as they study the past and look towards the future!

To find other Algebra II modules, go to Common Core Algebra II Statistics and Probability.

# Lessons

## Making Deviation Standard

In this lesson, you will begin by reviewing mean absolute deviation as a measure of variability. Your new learning will begin with standard deviation and understanding the difference between mean absolute deviation and standard deviation. This is critical for students who plan on advancing into higher level statistics courses.

> Go to Lesson: Making Deviation Standard

In this lesson, you will explore normal distributions and population percentages. You are introduced to normal distributions using a game simulator. Following this, you will work with skewed distributions and population percentages based on data about U.S. presidents. Unlike the first lesson in this module, this lesson is entirely new learning.