How many units are in AP Statistics? Five
By Jude Wallis · Published
AP Statistics has five units: Exploring One-Variable Data and Collecting Data; Probability, Random Variables, and Probability Distributions; Inference for Categorical Data: Proportions; Inference for Quantitative Data: Means; and Regression Analysis. The Fall 2026 redesign cut nine units to five.
The five units, their titles, exam weightings, class-period counts, and topic counts are the Fall 2026 AP Statistics course structure, first examined May 2027. Weightings are each unit's share of the multiple-choice section.
The five units, with weightings
The AP Statistics course effective Fall 2026, first examined in May 2027, has five units covering 55 topics between them.
| Unit | Title | Exam weighting | Class periods | Topics |
|---|---|---|---|---|
| 1 | Exploring One-Variable Data and Collecting Data | 20-30% | ~26 | 13 |
| 2 | Probability, Random Variables, and Probability Distributions | 15-25% | ~24 | 12 |
| 3 | Inference for Categorical Data: Proportions | 15-25% | ~30 | 15 |
| 4 | Inference for Quantitative Data: Means | 10-20% | ~18 | 10 |
| 5 | Regression Analysis | 10-20% | ~9 | 5 |
That is roughly 107 class periods across the year. Each unit page below has the full topic list:
The weightings are the multiple-choice section, not the whole exam
This is the detail most summaries drop. The percentages above are each unit's share of the multiple-choice section, which is itself 50% of the exam score. They are not shares of your overall grade.
The free-response section is organized a different way, around the four course practices rather than by unit, and its four questions are worth 12.5% of the exam each. So a unit at 10-20% of Section I is not the same as a unit worth 10-20% of your result.
Notice also that the ranges do not have to be tight. The five lower bounds add to 70% and the five upper bounds add to 120%, so no single exam can put every unit at the top of its range. Treat the ranges as bands the exam moves within, not as a fixed allocation.
Where the class periods do not match the weighting
Two units are out of proportion with their teaching time, and both are worth knowing about before you plan revision.
Unit 3 gets the most class periods of any unit, roughly 30, for a 15-25% share of Section I. It is the longest unit to teach because proportions inference is where confidence intervals, significance tests, errors, two-sample procedures, and chi-square all arrive at once, across 15 topics.
Unit 5 is the opposite. Regression Analysis is five topics in roughly 9 class periods, and it still carries 10-20% of Section I. Per topic that puts it at 2.00-4.00% of Section I, against 1.00-1.67% for Unit 3, so Unit 5 topics outweigh Unit 3 topics on every reading. Against Unit 1 the bands overlap and it is not settled either way. Either way it sits at the end of the year, where it is easiest to under-prepare.
It used to be nine units
College Board redesigned AP Statistics for the 2026-27 school year, and the old nine units became five. This is not a renumbering exercise. Content was cut as well as regrouped, and the removals are listed on College Board's AP Statistics future revisions page: five entries, including the geometric distribution, the chi-square goodness-of-fit test, and the whole of the old Unit 9 on inference for slopes. What was removed from AP Statistics works through all five, including the one about departures from linearity that is routinely over-read: what went is the topic on transforming data to straighten a curve, while reading curvature in a residual plot is still assessed under topic 5.4.
The numbering moved as well as the content. When a review book says Unit 4 is about random variables, or Unit 8 is about chi-square, it is describing the old course. In the current course, random variables are in Unit 2 and chi-square is in Unit 3.
Before you use any AP Statistics resource, check how many units it lists. Nine means it predates the redesign.
What each unit actually covers
In one line each:
- Unit 1 builds and describes distributions of one variable, then turns to how data get collected: sampling methods, what can go wrong with them, and experimental design.
- Unit 2 runs from two-way tables and probability rules through random variables to the binomial and normal distributions, ending at sampling distributions and the central limit theorem.
- Unit 3 is inference for proportions: confidence intervals, significance tests, errors, one and two samples, and the chi-square tests for homogeneity and independence.
- Unit 4 is the same machinery for means, including paired data and two-sample procedures.
- Unit 5 is scatterplots, correlation, linear models, residuals, and least-squares regression.
If you want the exam mechanics rather than the content map, what is on the AP Statistics exam sets out both sections, and the exam format page has the full breakdown.
Turning unit weightings into a question count
Section I is 42 multiple-choice questions, and unit weightings are shares of that section. Roughly how many multiple-choice questions should you expect from each unit?
Unit 1 at 20-30%: and , so about 8 to 13 questions.
Unit 2 at 15-25%: and , so about 6 to 11 questions.
Unit 3 at 15-25%: the same band as Unit 2, about 6 to 11 questions.
Unit 4 at 10-20%: and , so about 4 to 8 questions.
Unit 5 at 10-20%: the same band as Unit 4, about 4 to 8 questions.
Sanity-check the bands: the low ends total questions and the high ends total . Since the section has 42 questions, no exam can sit at the top of every range at once.
Roughly 8 to 13 questions from Unit 1, 6 to 11 each from Units 2 and 3, and 4 to 8 each from Units 4 and 5. Because the upper bounds add to more than 42 questions, some units land near the bottom of their band on any given exam.
Frequently asked questions
How many units are in AP Statistics?
Five, since the Fall 2026 redesign: Exploring One-Variable Data and Collecting Data; Probability, Random Variables, and Probability Distributions; Inference for Categorical Data: Proportions; Inference for Quantitative Data: Means; and Regression Analysis.
Did AP Statistics used to have nine units?
Yes. The course College Board replaced for 2026-27 had nine units. The nine were regrouped into five and some content was cut, so a nine-unit resource is not just organized differently, it covers topics the current exam no longer assesses.
How many topics are in AP Statistics?
55 across the five units: 13 in Unit 1, 12 in Unit 2, 15 in Unit 3, 10 in Unit 4, and 5 in Unit 5.
Which AP Statistics unit is worth the most?
Unit 1, Exploring One-Variable Data and Collecting Data, at 20-30% of the multiple-choice section. It is also the unit students most often treat as the easy opening stretch, which is a mistake at that weighting.
How long does each unit take to teach?
Roughly 26 class periods for Unit 1, 24 for Unit 2, 30 for Unit 3, 18 for Unit 4, and 9 for Unit 5, which is about 107 in total. Unit 3 is the longest to teach and Unit 5 the shortest.