H0: MA1 = MA2
= . . . = MAG (homogeneity of measures of association, indicating
no interaction)
H1: at least one MAi differs (indicating
interaction)
where MAi is a measure of association, either a strata-specific RR or OR
(B) Set alpha level
(C) Test statistic is a chi-square test for interaction (separate chi-square interaction statistics for relative risks and odds ratios). The p value is the probability region in right tail of Chi-square with G - 1 degrees of freedom, where G represents the number of strata tested. This statistic is computed with the TABLES E D C command.
(D) Conclusion: Reject H0 if p < alpha. A rejected null hypothesis indicates that the observed heterogeneity of effect (interaction) is significant.