The Homogeneity of Data

At the end of Chapter III on the comparison of means it was mentioned that complications arise in the calculation of standard deviations if the observations are not independent of each other. 

In general, with an analysis of variance between and within batches (One Factor with Replication) if we have m batches of n individuals then let us define 

It is evident that ot is always smaller than or = oa + ob , and the error will be greatest when ob /oa ten to 0 and when m is large and n = 2. Under these circumstances ot is only half ot , the correct value for the total variance. 

Consider the block of 30 observations discussed in Chapter VII (b), Analysis Between and Within Columns. Suppose we wished to calculate the standard deviation of the mean of these observations. 

If we ignored the fact that these 30 observations are not independent of each other, but are actually 10 groups, each group being 3 observations, we should calculate the variance from its ordinary definition which corresponds to terms (1) — (3) in that section divided by the total degrees of freedom, i.e. 203.87/29 = 7.030, and the standard deviation of the individual observations would be 2.65, and the standard deviation of the mean would be 2.65/ = 0.484. 

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The paper reports some of the initiatives undertaken in the field of chemical accidents of industrial origin. The accent was on the necessity to share available information between countries about the occurrence of the events and lessons learned. It is recognized that there is still the need to improve the harmonization of reporting tools towards the homogenization of data collection. The issue of possible transboundary effects of chemical accidents has not been covered in this report. However, a number of reporting and alert systems have been established in Conventions signed by representatives of several countries in Europe and world-wide. 

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