RTEI program (Randomization Tests for assessing Edge Influence) The RTEI program is an updated version of the Critical Values Approach program (Harper and Macdonald 2002) that was used by Harper and Macdonald (2011). The main difference is that RTEI includes edge and reference values in the randomization whereas the Critical Values Approach only included the reference values. RTEI for a single edge type is described in the accompanying article that introduces this program (Harper and Macdonald 2011). Here we present the instructions on how to use the program for a single-edge type. If you have any problems, questions, comments or suggestions about this program, please e-mail KarenHarper@eastlink.ca, Ellen.Macdonald@ualberta.ca, or firstname.lastname@example.org.