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One-tailed test in AP Statistics

A one-tailed test is a statistical hypothesis test that assesses the direction of a relationship or effect, determining whether a population parameter is greater than or less than a certain value.

Verified for the 2027 AP Statistics examLast updated August 2026

What is One-tailed test?

A one-tailed test is a statistical hypothesis test that assesses the direction of a relationship or effect, determining whether a population parameter is greater than or less than a certain value.

In AP Statistics, this term belongs to 3.5 Setting Up a Test for a Population Proportion and 4.4 Setting Up a Test for a Population Mean or Population Mean Difference. Use the notation and conditions attached to the procedure or model, then interpret the result in context.

Why One-tailed test matters in AP® Statistics

one-tailed test supports Unit 3: Inference for Categorical Data: Proportions and Unit 4: Inference for Quantitative Data: Means. The relevant CED learning objectives cover justify the appropriateness of a hypothesis test for a population proportion by verifying conditions; identify the null and alternative hypotheses for a population proportion.

How One-tailed test connects across the course

3.5 Setting Up a Test for a Population Proportion

one-tailed test is used in this topic. Connect the definition to the topic's calculations and interpretations in context.

4.4 Setting Up a Test for a Population Mean or Population Mean Difference

one-tailed test is used in this topic. Connect the definition to the topic's calculations and interpretations in context.

Is One-tailed test on the AP® Statistics exam?

An AP question can ask you to select, check, calculate, and interpret an inference procedure for proportions or categorical data; or select, check, calculate, and interpret a t-procedure for means. Name the concept precisely, show the relevant calculation when needed, and state the conclusion in the problem's context.

Key things to remember about One-tailed test

  • A one-tailed test is a statistical hypothesis test that assesses the direction of a relationship or effect, determining whether a population parameter is greater than or less than a certain value.

  • one-tailed test is mapped to 3.5 Setting Up a Test for a Population Proportion and 4.4 Setting Up a Test for a Population Mean or Population Mean Difference in the current AP Statistics course.

  • On an AP question, use one-tailed test as part of a complete calculation or interpretation, not as an isolated label.

Frequently asked questions about One-tailed test

What is one-tailed test in AP Statistics?

A one-tailed test is a statistical hypothesis test that assesses the direction of a relationship or effect, determining whether a population parameter is greater than or less than a certain value.

Which AP Stats unit covers one-tailed test?

one-tailed test appears in Unit 3: Inference for Categorical Data: Proportions and Unit 4: Inference for Quantitative Data: Means, especially 3.5 Setting Up a Test for a Population Proportion and 4.4 Setting Up a Test for a Population Mean or Population Mean Difference.

How does one-tailed test appear on the AP exam?

An AP question can ask you to select, check, calculate, and interpret an inference procedure for proportions or categorical data; or select, check, calculate, and interpret a t-procedure for means. Name the concept precisely, show the relevant calculation when needed, and state the conclusion in the problem's context.

Is one-tailed test only a vocabulary term?

No. Be ready to use it in a calculation, identify it in a setup, or interpret what it means in context.