Why this chapter matters
Descriptive statistics turn raw values into an interpretable picture and guide which models and tests are reasonable next.
What you will learn
- Choose suitable visual summaries for categorical and quantitative variables.
- Compute and interpret mean, median, quartiles, range, and standard deviation.
- Describe distribution shape, skew, and potential outliers in context.
Lessons in this chapter
- Tables and graphs for distributionsBuild frequency tables, bar charts, histograms, and boxplots correctly. Read the full guide →
- Measures of centerCompare mean and median under symmetric and skewed data patterns.
- Measures of spreadUse IQR and standard deviation to quantify variability.
- Shape and outlier interpretationWrite clear distribution summaries that include center, spread, shape, and unusual points.
Study task
Given a weekly study-hours dataset, create a histogram and boxplot, compute center and spread, and write a four-sentence distribution summary.
Chapter checkpoint
When might median be preferred over mean as the center measure?
When data are strongly skewed or contain outliers, because median is less affected by extreme values.