With observational data, we can implement the propensity score matching. Which of the following statements is false abou

[answerhappygod]

With observational data, we can implement the propensity score
matching. Which of the following
statements is false about the propensity score matching?

a) The propensity score matching finds similar observations in
terms of the propensity score.
b) The propensity score refers to the probability of being
treated for each subject.
c) The propensity score matching automatically detect the lack of
common support.
d) The propensity score matching always use all observations to
estimate a treatment effect.