Welcome to the fourth edition of *A Portable Introduction to Data Analysis*.

This is a major revision of the textbook, including new sections on designing studies and power analysis, as well as smaller sections on topics such as scientific hypotheses, information theory, and maximum likelihood estimation. The presentation of most other sections has been extensively revised. Summaries are now included at the end of each section, along with many new exercsies, and new data sets have been added at the back of the book.

#### 2010 Version

For 2010 the textbook was produced in a new version that was more soft and slender (22% thinner) than the original but with the same content. Unfortunately this edition is no longer available.

#### Data Sets

You can copy the data sets directly for use in OStats and R.

#### Exercise Solutions

Solutions to some exercises are available.

#### Errata

Visit the page of errata to read about any notes or corrections for the fourth edition.