The dummy variables for presence of state bargaining laws covering public employees and presence of state right to work laws in the datafile provide an opportunity to examine a two-predictor regression involving dummy varia- bles. In this case there is interaction between the two dummy variables and this calls for interpretation. The interaction variable forms a two-way class- ification table and the regression equation estimates the means of the obser- vations in the four cells. In the current case the main effect of right-to-work laws is not significant, but the interaction with comprehensive state bargaining laws is. The presence of right-to-work laws is said then to modify the relation between unionization and state bargaining laws covering public employees. Right-to-work laws would be termed a moderator variable.