ProUCL version 5.1.002 (5.1) is the latest update of the ProUCL statistical software package for analysis of environmental data sets with and without nondetect (ND) observations. The ProUCL software is available at https://www.epa.gov/land-research/proucl-software. This final installment of the three part ProUCL e-learning seminar will focus mainly on background dataset analysis and associated background threshold value (BTV) comparisons within the ProUCL software. General discussion points will include Background dataset analysisAppropriate sample size selectionUTLs and background threshold valuesComparison of BTVs to site dataA ProUCL provided background environmental dataset (XLS) will be used as an example throughout the presentation. This dataset is provided here and it is encouraged for attendees to follow along on their local machine. To view this archive online or download the slides associated with this seminar, please visit http://www.clu-in.org/conf/tio/ProUCLAtoZ3_030920/