Free study guide · all 9 units · plain words a 5th grader would get
AP Stats, made simple
Every big idea in AP Statistics, explained like a friend would explain it. Play with the ideas in the lab, practice for the exam, and ask the AI tutor anything.
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The nine units
Everything on the AP exam, one unit at a time. Each one says how much of the exam it covers. Open a unit for the big ideas, an everyday example and the mistake to watch for.
The stats lab
Ideas stick better when you can poke them. Drag, click and press the buttons to watch statistics happen.
Unit 1 · z-scores
How much of the curve is shaded?
A z-score says how many standard deviations (steps) you are from the middle. Slide it and watch the shaded part. The shaded area is the percent of values in that part.
Unit 5 · central limit theorem
Grab samples, graph their means
The top picture is the whole population. Each sample grabs n values and finds their mean. The bottom graph collects those means. Watch it turn into a bell, even when the top isn't one.
Unit 6 · confidence intervals
How often does the net catch the fish?
Pretend we know the truth: 60% of all students like pizza best. Each line is one sample's confidence interval. Purple lines catch the true 60%. Orange lines miss it. About 95% of 95% intervals should catch it.
Unit 2 · regression
Click to add dots, watch the line
Click or tap the graph to add points. The line of best fit and the correlation r update each time. Try adding one far-away point and see how much it pulls the line.
Which test do I use?
Every inference question on the exam uses the same four steps: State, Plan, Do, Conclude. First ask what kind of data you have.
- Yes/no answers?Percents: use a z-test for proportions.
- Numbers you can average?Means: use a t-test.
- Counts in many categories?Use a chi-square test.
- A line through dots?Use a t-test for the slope.
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Quick check
Exam-style questions with the reason behind every answer. Pick a unit or do them all.
Cheat sheet
The formulas you'll use most, each with what it means in plain words. You get a formula sheet on the exam, so focus on knowing when to use each one.
Key terms
Stats words in plain English. Underlined words in the lessons open these too.
No key terms match that word yet. Try asking Stat Buddy.
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How it's made
The lessons, examples and practice questions were written with Claude, an AI model made by Anthropic, following the nine units of the AP Statistics course. The goal is plain words: if a 5th grader could follow the sentence, it stays.
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