Introduction to the t-test
Content for Thursday, February 4, 2027
Goals
By the end of this topic, you should be able to:
- Explain why estimating σ leads to t, and what df does
- Run a one-sample t-test
- Report Hedges’ g and a confidence interval
- Keep statistical and practical significance apart
Reading
- Before session 1: sections 9-1, 9-2 and 9-4.
- Before session 2: section 9-3. Skip r² as an effect size.
NoteThe book and our slides
- The book: writes the estimated standard error as s_M. Our slides: write σ̂_M.
- The book: calls the effect size estimated Cohen’s d. Our slides: call it g. d is the population value, and g is its estimate.
- The book: writes an interval as μ = M ± t s_M. Our slides: say it’s an interval for μ: from M − t σ̂_M to M + t σ̂_M.