General ⇒ How to write this formula

[gmedina]

Please read our previous responses and the links to basic documentation. Regarding the spacing issue here's another option:

Code: Select all

\documentclass{beamer}
\usepackage{amsmath}

\newcommand\mypar{\par\vspace{\baselineskip}} 

\begin{document}

\begin{frame}
\begin{equation*}
  \begin{split}
  \alpha_{\text{act}}^{\text{recalc}}=
  &\sum_{x_{11}=0}^{n_{11}}\sum_{x_{12}=0}^{n_{12}}\sum_{x_{21}=0}^{n_{21}}\sum_{x_{22}=0}^{n_{22}}
  \binom{n_{11}}{x_{11}}\binom{n_{12}}{x_{12}}\\
  &\times\binom{n_{21}}{x_{21}}\binom{n_{22}}{x_{22}}
  \pi^{x} \, (1-\pi)^{n-x}\cdot 1_{\left\{\chi^{2}\geq\chi^{2}_{1,1-\alpha}\right\}}
  \end{split}
\end{equation*}
\end{frame}

\begin{frame}
  Some text

  Some text

  Some text\mypar

  Some text
\end{frame}

\end{document} 

EDIT: Ah! I think then that this post can be safely deleted.

On a second thought, maybe not. I will leave the decision to the Moderators