Stats 1: Foundations
This is the front door. Thirteen lessons take you from your first bar chart to your first t-test, and each one pairs a plain-language explanation with an interactive you can drag until the idea clicks.
No stats background is assumed, and no formula appears before the picture it describes. The spine of the course is one story: how a handful of honest descriptions of data (means, spreads, shapes) turn into tools for reasoning about people you never measured. Sampling distributions and the central limit theorem carry that story, and hypothesis testing and confidence intervals finish it.
Work through it in order if you're new; each lesson leans on the ones before it. If you studied statistics years ago and just want the rust off, jump straight to section 1.7 and let the sampling machinery surprise you again. When you're done, Stats 2 continues with ANOVA, correlation and regression.