Statistical Method
 Regression Discontinuity and Interrupted Time Series analysis has long confused me. I found a presentation of University of Washington that discusses the differences. It is almost the only place that I found this information. It seems like the biggest difference is that ITS relies on population data and RD on individual data. Overall RD is more robust than ITS.
Latex
 Conditional equations in Latex. Answers from here.

\[ f(x)= \begin{cases} \frac{x^2x}{x},& \text{if } x\geq 1\\ 0, & \text{otherwise} \end{cases} \]
However, This code generate equation without numbering. To change it, we remove \[ and \] and replace with \begin{equation} and \end{equation}. Another thing to modify is when we write functions this why, the format of \sum becomes its inline format – the beginning and end of the range of independent variable appears to the right of the capital sigma. To change that, use \sum\limits_{i=1}^{m_y} instead of \sum_{i=1}^{m_y}.