AP Statistics · Exam guide
AP Statistics FRQ Guide: How Free-Response Answers Are Scored
The free-response half of AP Statistics is 50 percent of your score, and it rewards one thing above all: statements in context. The exam has 42 multiple-choice questions and 4 free-response questions, and the last free-response question is an investigative task that pulls from several units at once. This guide shows how answers are scored and gives you a habit that earns points on almost every question.
How the questions are scored
Each question is split into parts, and each part is judged essentially correct, partially correct, or incorrect. Those judgments add up to the score for the question. Graders read what you wrote, not what you meant, so a correct number with no explanation usually earns only partial credit.
Four things graders look for
| Look for | What it means |
|---|---|
| Method | You name the right procedure (a one-sample t interval, a chi-square test) and say why it fits the situation. |
| Conditions | You check the conditions for that procedure with facts from the problem, not just the words "random" and "normal". |
| Mechanics | The numbers are right: the statistic, the standard error, the degrees of freedom, the probability. |
| Conclusion in context | You state the result using the variable and population of the problem, and you link the decision to the evidence. |
The four-step habit: State, Plan, Do, Conclude
- State: say what parameter you are estimating or testing, in words and with the population.
- Plan: name the procedure and check the conditions using the information in the problem.
- Do: show the statistic, the standard error or degrees of freedom, and the interval or p-value.
- Conclude: answer the original question in context, and connect the decision to the number.
A worked confidence interval (made-up data)
A school counselor surveys a random sample of 50 students from a large school. The mean sleep time is 7.2 hours with a standard deviation of 1.1 hours. The sample is random and the size is large enough for the interval to be reasonable (n of 50 is at least 30). Estimate the mean sleep time with 95 percent confidence.
| Piece | Work |
|---|---|
| Standard error | 1.1 divided by the square root of 50 is about 0.156 |
| Critical value | t* with 49 degrees of freedom is about 2.010 |
| Margin of error | 2.010 times 0.156 is about 0.313 |
| Interval | 7.2 plus or minus 0.313 gives about 6.89 to 7.51 hours |
It never says what the mean is the mean of, so the conclusion is not in context.
It names the parameter and the population, and states the confidence level the way the exam expects.
The investigative task
The last question is longer and mixes ideas, for example a study design, a comparison, and an inference in one situation. Treat each lettered part as its own small question, and do not skip a part because you could not finish the one before it. Partial credit is available part by part.
Common mistakes
- Writing "we reject the null" without saying what that means for the situation in the problem.
- Describing a p-value as the probability the null hypothesis is true. It is the chance of a result this extreme if the null were true.
- Claiming cause and effect from an observational study. Only a randomized experiment supports it.
- Skipping the conditions, or checking them with a generic phrase instead of the problem's facts.
- Giving a number without units or without comparing it to the question.
Frequently asked questions
How many free-response questions are on AP Statistics?
Four, and the last one is an investigative task that draws on several units. The free-response section is half of your exam score.
Do I have to show my work?
Yes. Graders award credit for the method, the conditions, the calculation and the conclusion, so a bare number can earn only part of the points.
Can I use my calculator?
Yes, but name the procedure and write the setup. A calculator result with no statement of the test or interval is hard to credit.
What does "in context" mean?
Use the actual variable, units and group from the problem. "The mean" is not in context. "The mean nightly sleep time for students at this school" is.
Where can I find the official scoring rules?
Exam formats change a little from year to year, so check the current course and exam description on the College Board site before test day.
Keep practicing
Every unit in the AP Statistics course ends with a ten-problem practice set, three multiple choice and seven free response, with worked answers. These free lessons also build the skills the free-response section tests:
See the AP Statistics course Free lessons and lesson list
Other free-response guides:
AP is a registered trademark of the College Board, which is not affiliated with and does not endorse this site. This guide is our own explanation of the question types and scoring. For the official scoring guidelines, see the College Board.