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Fig. 1 | BMC Medical Research Methodology

Fig. 1

From: Minimizing bias in massive multi-arm observational studies with BCAUS: balancing covariates automatically using supervision

Fig. 1

Schematic of BCAUS. Structured data composed of control and treatment instances is fed to a neural network. The output of the network p(i) for each instance i is a propensity score that optimizes a combination of two loss functions. A The binary cross entropy loss \( {\mathcal{L}}_{BCE} \) is computed by comparing p(i) against targets t(i) = 0 for control and t(i) = 1 for treatment. B The bias loss \( {\mathcal{L}}_{B\mathrm{I} AS} \) is computed as follows: (i) p(i) is used to compute an inverse probability weight (IPW, orange box) that multiplies all covariates of instance i (ii) weighted means \( {\overline{x}}_j \) are computed separately for treatment and control groups for each covariate xj, and (iii) the mean squared error between weighted means of treatment and control covariates defines the bias loss. The sum of both losses is computed and backpropagated. μ is the scalar ratio of \( {\mathcal{L}}_{BCE} \) to \( {\mathcal{L}}_{BIAS} \) that is detached from the computation graph. The relative contribution of each loss component is tuned using hyperparameter, ν

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