IMPLICATION OF CORRELATIONS AMONG SOME COMMON STABILITY STATISTICS - A MONTE-CARLO SIMULATIONS

Stability analysis of multilocation trials is often based on a mixed t wo-way model. Two stability measures in frequent use are the environme ntal variance (S-i(2)) and the ecovalence (W-i). Under the two-way mod el the rank orders of the expected values of these two statistics are identical for a given set of genotypes. By contrast, empirical rank co rrelations among these measures are consistently low. This suggests th at the two-way mixed model may not be appropriate for describing real data. To check this hypothesis, a Monte Carlo simulation was conducted . It revealed that the low empirical rank correlation among S-i(2) and W-i is most likely due to sampling errors. It is concluded that the o bserved low rank correlation does not invalidate the two-way model. Th e paper also discusses tests for homogeneity of S-i(2) as well as impl ications of the two-way model for the classification of stability stat istics.