Fig. 2: Relative Index of Inequality and Slope Index of Inequality between the control and intervention groups.

RII (y-axis) and SII (x-axis) are the two major measures in epidemiological studies for quantification of inequalities in relative and absolute scales, respectively. These are regression-based indicators which use all subgroups compared to a pairwise comparison that ignores other groups. To estimate these indices, we first ranked the individuals from those with the lowest socioeconomic position (rank = 0) to those with the highest socioeconomic position (rank = 1) in the cumulative distribution of the wealth index. We used a generalized linear model using a binomial family with a log link. We calculated the RII as the ratio of the value at the bottom of the socioeconomic position (intercept) to the value at the top (intercept + slope). Meanwhile, the SII is the difference between the value at the bottom of the socioeconomic position (intercept) and the value at the top (intercept + slope). RII = 1 and SII = 0 indicate no inequality. RII > 1 and SII > 0 indicate inequality disfavoring the participants with the lowest socioeconomic position (i.e., child diarrhea is more concentrated among the participants with the lowest socioeconomic position). The central estimates as depicted by circles represent the RII (y-axis) and SII (x-axis). Error bars represent 95% confidence intervals. Please refer to Table 2 for the sample size details (n = 8440 observations).