Choosing statistical tests: part 12 of a series on evaluation of scientific publications.

BACKGROUND: The interpretation of scientific articles often requires an understanding of the methods of inferential statistics. This article informs the reader about frequently used statistical tests and their correct application.

METHODS: The most commonly used statistical tests were identified through a selective literature search on the methodology of medical research publications. These tests are discussed in this article, along with a selection of other standard methods of inferential statistics.

RESULTS AND CONCLUSIONS: Readers who are acquainted not just with descriptive methods, but also with Pearson's chi-square test, Fisher's exact test, and Student's t test will be able to interpret a large proportion of medical research articles. Criteria are presented for choosing the proper statistical test to be used out of the most frequently applied tests. An algorithm and a table are provided to facilitate the selection of the appropriate test.