Common Mistakes in AP Statistics

Many students lose points on the AP Statistics exam for simple, avoidable errors. Being aware of these common pitfalls can help you secure a higher score.

Conceptual and Communication Errors

Confusing correlation with causation. State that association does not imply causation unless the data comes from a well-designed, controlled experiment.
Forgetting to check conditions for inference. For every confidence interval or hypothesis test, explicitly list and verify the required conditions (e.g., Random, 10%, Large Counts).
Describing a distribution with only the mean. Always address Shape, Outliers, Center, and Spread (SOCS) when asked to describe or compare distributions.
Misinterpreting a p-value. Define the p-value as the probability of observing a result as or more extreme than yours, assuming the null hypothesis is true.
Using non-specific language. Always refer to the context of the problem. Instead of 'the mean is higher,' write 'the mean height of students in Group A is higher.'
Stating hypotheses about sample statistics. Write hypotheses using population parameters (like μ, p, β), not sample statistics (like x̄, p̂, b).