1. Soil Analysis Methods Accuracy and Precision Comparison: Historical North American Proficiency Testing (NAPT) Program Results

The SSSA-NAPT Program provides open access to soil, water, and plant laboratory data. This data is collected quarterly from about 150 participating laboratories. For soil data, five samples are sent to participant laboratories for them to submit data for any or all of the 99 accepted methods. Our objective was to evaluate data precision from 43 soil samples (2019-2021). A measure of precision was made by dividing the Median Absolute Deviation (MAD) by the Median for each of the 43 samples... B.G. Hopkins, G.E. Cardon, J.R. Lawley