Dear Monica: To calculate Diffraction Precision Index (DPI) and individual atomic coordinate errors:
You could either go through the IUCrJ article entitled "Do we see what we should see? Describing non-covalent interactions in protein structures including precision" (http://journals.iucr.org/m/issues/2014/01/00/mf5001/index.html) and preform a back-of-the-envelope calculation using equation 1 and 2 or more conveniently just use the Online_DPI web-server (http://cluster.physics.iisc.ernet.in/dpi/) Reference: J. Appl. Cryst. (2015) 48, doi:10.1107/S1600576715006287. I hope that answered your question. Cheers, Gurusaran M, Research Assistant, Supercomputer Education and Research Centre, Indian Institute of Science, Bangalore, India.