Pilot edition, Spring 2027. This version of the book is being tested in a few sections and changes during the semester.

Unit 3: Proportions and Means

The unit opens with the normal curve as a model for individual values, such as heights or test scores. After that, each chapter takes one method: one proportion, two proportions, one mean, two means, or paired data. Each works the method three ways:

1. Simulate it on the chapter’s data.
2. Model it with the formula that shortcuts the simulation.
3. Compare the two, including a case where the shortcut breaks down.

By the end you’ll have the \(z\) and \(t\) procedures, and you’ll know when to trust them.