The 3rd Edition of *OpenIntro Statistics* was released in July 2015.
Below are the main changes:

- The t distribution is used exclusively in the Inference for Numerical Data chapter (Ch 5).
- Some data sets are replaced with newer or more interesting data sets.
- Some exercises are revamped, and some entirely new exercises have been added. The number of exercises has increased by a small amount.
- Video icons were added to sections where videos are available, and these are hyperlinked in the PDF.
- Section 8.2, which focuses on variable selection in multiple regresion, now highlights the usage of adjusted R-squared instead of p-values for variable selection. Both approaches are still featured, but adjusted R-squared is featured more prominently.
- Section 3.2.2 in the Second Edition, which covers calculations for the normal probability plot, was eliminated. Additionally, the R function qqline() is now used throughout the textbook for the normal probability plot, whereas a custom function was previously used.
- The within-text exercises (the ones with solutions in the footnotes)
are now called
*Guided Practice*to eliminate duplicate "exercise" numbering with end-of-chapter exercises. - We dropped the df > 1 condition for the chi-square test. The reasoning on why it was introduced is subtle: a 1-prop test can be turned into a chi-square test with df = 1, but then we only need 5 successes / failures for the 2-prop test, so the conditions don't match. Anyways, we removed this condition for simplicity.
- The section on calculating power (Section 4.6) was removed and a new section was added in Chapter 5 that covers power in the context of an experiment. This new section should be much easier to follow, and the example is also a much more common power calculation context.
- A reference to Why 0.05? was added.
- There were other minor changes, e.g. fixing typos identified in the Second Edition.

Full details of all updates are logged in
GitHub.
To explore, review the *Commits* feed.

If you have questions related to the Third Edition, see this thread in the Public Forums and ask away!

**Still want to use the 2nd Edition this next year?**
The 2nd Edition will continue to be available as a PDF
in the Archive section on the Textbook page,
and we will contiue to sell paperbacks of this edition on Amazon until
May 2016. However, do be aware that students may accidentally
access or purchase the 3rd Edition, so if you are using the
2nd Edition, please very clearly tell them to download and/or
purchase the older edition. Short links to help keep things straight:

- openintro.org/os2
- openintro.org/os2/amazon

For reference, there are also short links to the Third Edition by dropping the "2" in the Second Edition URLs:

- openintro.org/os
- openintro.org/os/amazon