Module 2: Descriptive Statistics
Learn to summarize and describe data using numbers! Discover how to calculate and interpret measures of center, spread, and distribution shape.
Prerequisite: Module 1
This module builds on concepts from Module 1: Introduction to Statistics & Data. You should understand types of data (quantitative vs. qualitative, discrete vs. continuous) before starting Module 2.
Your Progress
Learning Objectives
By the end of this module, you will be able to:
- Calculate and interpret measures of center (mean, median, mode) for different datasets
- Calculate and interpret measures of spread (range, IQR, variance, standard deviation)
- Identify and describe distribution shapes (symmetric, right-skewed, left-skewed)
- Create and interpret five-number summaries and boxplots
- Choose appropriate measures based on data characteristics and distribution shape
Why This Matters
Numbers tell stories! When you see headlines like "Average salary for college graduates" or "Test scores improved," descriptive statistics are at work.
This module teaches you to:
- Summarize large datasets with just a few meaningful numbers
- Understand what "average" really means (and when it's misleading)
- Describe data variability and why it matters
- Compare groups using statistical measures
- Identify outliers and unusual observations
- Make informed decisions based on data summaries
Get Started: Pre-Assessment
Before You Begin...
Take a quick 5-question pre-assessment to see what you already know about descriptive statistics. This isn't graded—it's just to measure your starting point.
Why do this? At the end of the module, you'll retake the same assessment and see how much you've learned!
Recommended: Take the pre-assessment! It only takes 5 minutes and helps you track your learning.
Module Lessons
Measures of Center
Learn to calculate mean, median, and mode—the three ways to describe the "center" or "typical value" of a dataset. Discover when to use each measure.
25-30 minutes
Measures of Spread
Explore range, interquartile range (IQR), variance, and standard deviation. Learn why understanding data variability is just as important as knowing the average.
30-35 minutes
Distribution Shapes and Skewness
Discover how to describe the shape of a distribution. Learn about symmetric, right-skewed, and left-skewed distributions and how shape affects which measures to use.
25-30 minutes
Five-Number Summary and Boxplots
Master the five-number summary (Min, Q1, Median, Q3, Max) and learn to create and interpret boxplots—powerful visual tools for comparing distributions.
25-30 minutes
After the Lessons
Practice Problems
Apply what you've learned with 20 practice problems covering all module topics. Calculations, interpretations, and real-world applications!
Practice ProblemsModule Quiz
Test your understanding with a 15-question quiz. Pass with 70% to earn your Module 2 badge!
Take Module QuizStudy Materials
Download printable study guides with all formulas and quick reference cards. Perfect for exam prep!
AI Tutor Help
Stuck on a calculation? Need help interpreting results? Chat with the AI statistics tutor for personalized guidance.
Get AI HelpTips for Success
- Practice calculations - Descriptive statistics involves math! Work through examples step-by-step.
- Use a calculator - You're learning concepts, not arithmetic. A calculator helps you focus on understanding.
- Focus on interpretation - Calculating numbers is just the first step. Understanding what they MEAN is the goal.
- Check your work - Does your answer make sense? Mean should be between min and max. SD can't be negative!
- Connect to Module 1 - Data types matter! These measures work differently for different types of data.