Difference-in-Differences, https://diff.healthpolicydatascience.org/ (Last access: 2020/07/24) The quantity we care about. (興味のある対象) The algorithm that takes data as input and produces a value of the estimand. (Estimandを求めるために用いられるアルゴリズム・関数) The estimator’s output, given data input. (Estimatorの出力・実現値)