The Sloan Digital Sky Survey (SDSS) is a multi-year campaign to make a long series of astronomical observations consisting of spectra and photometry. This long effort has accumulated large amounts of data, and the sequential collections of data have been released over the course of the project. This article describes research using statistical tests which investigate how consistent later releases of the SDSS data are, compared to earlier releases. This line of work is important for many astronomers using various SDSS data sets.