Where AP Statistics begins. Tell categorical from quantitative variables, display them the right way, and describe a distribution by its shape, center, spread, and outliers. Then learn how to collect trustworthy data through random sampling and well-designed experiments.
Six ways to master Unit 1 — pick whichever fits how you like to study.
All 13 topics from the College Board CED, in order.
Unit 1 is the largest unit on the exam and the foundation for everything that follows. It splits into two big ideas. First, exploring one-variable data: you learn to tell categorical variables from quantitative ones, choose the right display for each (bar charts and pie charts for categorical; dotplots, stemplots, and histograms for quantitative), and describe a distribution by its shape, outliers, center, and spread (SOCS). You'll compute and compare summary statistics — mean, median, range, IQR, and standard deviation — and know which are resistant to outliers.
Second, collecting data: because a conclusion is only as good as the data behind it, you study random sampling (simple random, stratified, cluster, and systematic samples), the bias that creeps in when sampling goes wrong, and the principles of experimental design — control, randomization, and replication — that let you argue for cause and effect.
This unit is 20–30% of the AP Statistics exam and takes about 26 class periods. The four statistical practices below run through every topic: