Difference Bias Std.error* 95% CI
High socioeconomic status        
      ATT -0.63 -0.002 0.122 (-0.8823,-0.2166)
Low socioeconomic status        
     ATT -0.32 -0.0032 0.062 (-0.4542,-0.2283)
*std error are estimated by bootstrap method
Table 3: Average treatment effect among the treated (ATT) according to socioeconomic status.