Stratum

In an analysis of variance calculated by ANOVA, a stratum is produced for every term in the formula specified by the BLOCKSTRUCTURE directive. There is thus one for each of the sources of random variation in the design. Genstat automatically discovers which treatment terms are estimated in each of the strata. (Strata is the plural of stratum.) The total sum of squares in each stratum is then partitioned into the sums of squares for the treatment terms estimated in the stratum, and a residual which provides an estimate of variability against which these treatment sums of squares should be compared. This ensures that each treatment line in the analysis of variance table is automatically compared with the correct residual.