abstract: The present paper concerns interactions between a set of objects, where the same components (fractions) can be isolated, and a standard object, which consists of arithmetical mean shares in these fractions. A method was proposed how to estimate the variability observed in the structure of a given object, as compared with the standard structure, as calculated with a coefficient of compatibility with the standard (CCS). According to the algorithm introduced, the coefficient value falls between ( 0.1). When the structure of a given object is identical with the one of the standard, the coefficient amounts to 0.5. If a growth in cumulative interest for respective fractions is more intensive as compared with the one of the standard, the coefficient amounts to less than 0.5, otherwise the coefficient is higher than 0.5. Applying the method presented, it was observed that the sowing material in the majority of pea cultivars, researched by the Centre for Cultivar Testing (COBORU) in 1995, showed seed size structure si