4.11 Monthly Sr9° Levels in Powdered Milk from Perry, New York Since April 1954, S-pound cans of powdered whole milk have been sent to HASL each week from a milk powdering plant at Perry, New Yorke Table 11 summarizes the data in pyc Sr70/gram Cao are graphed in Figure 7. The data The values through December 1955 represent monthly averages of weekly samples, the error term representing one standard deviation from the mean. The monthly values for the year 1956 represent on analysis and a standard error of counting since the weekly samples were pooled each month, Starting January 1957, the monthly composites have been analyzed in replicate, the values thus being an average and the error term one standard deviation from the mean. - 82 «