Regression Discontinuity Design Result

Question

I am reading a paper on Voting Technology by Fujiwara (2015). He uses an RDD to estimate the causal effect. In his result tables, he mentions a stat named "Pre-treatment Mean", which I don't know the meaning of. He defines it in the footnote as "The pre-treatment mean is the estimated value of the dependent variable for a municipality with 40,500 registered voters that use paper ballot. Can someone explain what pre-treatment mean is and how it is calculated?

Answer 1

Pre treatment mean is simply the mean estimate of a variable before treatment was implemented.

There isn't a single way to estimate mean so there isn't a single way to estimate pre-treatment mean. A simplest estimator for a mean is: $\bar{x}= \sum_i^n \frac{x_i}{n}$.

Depending on context some other estimator for mean can be used.