Collaborative Testing among Laboratories Routinely Testing Fat and Protein in Milk

One of 19 laboratories chosen as a central lab uses a system of self observation and sends out reference and control samples to the remaining laboratories. Comparability of analyses has been improving gradually since 1974. Percentage of deviations exceeding .1% of protein was reduced from about 39% to .7%. The reduction for fat was 37% to 4.2%.