This book explores the impact of blocking sources of heterogeneity on the accuracy of contrast estimation in various experimental situations. The indicators of estimation accuracy selected for analysis include the relative efficiency of the RE design and the degree of change in confidence intervals I1/I2. The relationship between these indicators is determined by both the parameters of the alloy and the level of heterogeneity in the experimental material. Key parameters of the design include the number of main factors (I), the number of blocked sources of heterogeneity (K), the number of levels (n), and the number of replications (m).