The left side represents a standard BK-Plot, where the diagonal lines correspond to the probabilities of outcome in two randomization groups as a function of the fraction of subjects with the unobserved binary variable. The right side depicts a modified BK-Plot, where the outcome measure is plotted as a function of the fraction of subjects with the unobserved binary variable. We assume no interaction between the unobserved binary variable and treatment effect on the probability of outcome. Graphically, this means that we created BK-Plots so that the outcome measure has the same value at the leftmost and rightmost points. DIF = absolute difference; RR = relative risk; OR = odds ratio.
Baker and Kramer BMC Medical Research Methodology 2003 3:10 doi:10.1186/1471-2288-3-10