Welcome to Part 3 — Statistical Design of this free online high school statistics textbook. This practical section focuses on one of the most important skills in statistics: choosing the right statistical test for a given research question or scenario. Through decision-oriented lessons, real-world examples, and guided exercises, high school students learn how to evaluate study designs, identify appropriate descriptive and inferential methods, and avoid common pitfalls in statistical planning—essential preparation for AP Statistics, college-level courses, and real data analysis.
Part 3 bridges theory from earlier sections to applications, emphasizing experimental design, hypothesis formulation, variable types, sample size considerations, and test selection. Ideal for learners seeking to master statistical test selection, research design, and study planning in an intuitive, step-by-step format with free resources and interactive decision tools.
Lessons in Part 3: Statistical Design
- Formulating Research Questions and Hypotheses – Crafting clear statistical questions and null/alternative hypotheses with practical examples.
- Identifying Variables and Scales – Determining independent/dependent variables, scales of measurement, and their impact on test choice.
- Choosing Between Descriptive and Inferential Statistics – When to summarize data vs. draw conclusions about populations.
- Selecting the Right Test for One or Two Samples – Decision guide for t-tests, z-tests, and non-parametric alternatives.
- Tests for Multiple Groups and Relationships – Flowcharts and criteria for ANOVA, correlation, regression, and chi-square tests.
- Experimental vs. Observational Designs – Randomization, control groups, confounding variables, and ethical considerations.
- Sample Size and Power Basics – Understanding why sample size matters and simple rules for adequate power.
- Common Design Pitfalls and How to Avoid Them – Real-world cases highlighting errors in planning and interpretation.
>