@statsepi @ashtroid22 @Epi_D_Nique @healthstatsdude @stephensenn (1/n) The problem Senn is referring to here, was solved by Mindel C. Sheps in NEJM in 1958. I proposed a counterfactual causal model that formalizes the intuition behind her argument in this paper: degruyter.com/view/j/em.2018… @statsepi @ashtroid22 @Epi_D_Nique @healthstatsdude @stephensenn (2/n) Consider this example: If people both Russia and Norway are randomized to play Russian Roulette at the end of every year, and the baseline risk of death in a year i 0.5% in Norway and 1.0% in Russia: Calculate how many people will die in the active arm in each country.