The data for the means (weighted averages), the average absolute difference from the settlement pol, the total number of discards, and the number of times the result was furthest from the settlement value, indicate that the pol results of the buyer, seller and NYSTL are closer together and the performance of the laboratories are more comparable after the change over to the non-lead procedure. The above conclusions are confirmed by the ANOVA using all the individual polarization values for each time period. The results of this ANOVA show that with the old procedure there was a statistically significant difference between laboratories while with the current non-lead procedure there are no statistically significant differences between laboratories for the data investigated.
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