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Magruder Check Sample Program

"Round robin" samples are frequently used to provide comparisons of analytical results. The first program using statistical techniques to evaluate fertilizer sample results was the Magruder Check Sample Program. 

Each subscribing laboratory receives one or two samples each month. These samples typically contain varying levels of the primary nutrients (N, P, & K) as well as secondary (Ca, Mg & S) and many micro-nutrients of interest.

In addition, requests for analysis of contaminants of interest, including trace metals (As, Cd, Cr, Co, Hg, Pb, Ni, & Se) are often requested. Samples are analyzed according to methods chosen by the participating laboratory. The results, with method designations are reported directly to the statistician. A comprehensive statistical report is prepared, noting inter-laboratory bias and precision, with a coded ranking of individual laboratories. These reports are sent to subscribers for performance evaluation. Laboratories are identified only by number, with laboratory identification and performance held in strict confidence.