How do I move my sentences up close the title?

Question

I am using Share Latex site to create slides for my presentation.

I have the following codes:

\documentclass{beamer}
\usetheme{CambridgeUS}
\usepackage{graphicx}
\usepackage{mathabx}

\title{}
\author{}
\institute{}
\date{}

\begin{document}

\begin{frame}
\titlepage
\frametitle{} 
\end{frame}

\begin{frame}
\begin{center}
\frametitle{Outline}
\end{center}
\begin{itemize}
\item Introduction
\item Model 1
\item Main Results
\begin{itemize}
\item Graphical Analysis
\end{itemize}
\item Model 2
\item Main Results
\begin{itemize}
\item Graphical Analysis
\item Comparative statics
\end{itemize}
\item Conclusion
\item Appendix 
\end{itemize}
\end{frame}

\begin{frame}
\begin{center}
\frametitle{Introduction}
\end{center}

\begin{itemize}
\item Academic dishonesty is a serious issue in many developing countries.
\begin{itemize}
\item Cheating in school is a social norm. 
\item Generally, the professors do not take this issue seriously.
\item Low-level of punishment for the perpetrators.
\end{itemize}
\item The objective is to capture a student's decision to either plagiarize or be honest with two prisoner's dilemma models.
\end{itemize}
\end{frame}

\end{document}

I have this slide:

How do I move my sentences up and I also want to create spaces between the sentences?

Answer 1

You need to add the [t] option to your frames to align the text to the top of the frame. You can use the enumitem package to control the spacing of the itemized lists as shown in this answer, but you have to restore the default bullets after you do so, as explained here. Also, as mentioned in a comment, you should not put the frametitle in a center environment.

\documentclass{beamer}
\usetheme{CambridgeUS}
\usepackage{enumitem}
\setitemize{itemsep=20pt,% Change the item separation here
label=\usebeamerfont*{itemize item}% These lines are necessary to restore the bullets to each item
\usebeamercolor[fg]{itemize item}%
\usebeamertemplate{itemize item}%
}

\begin{document}

\begin{frame}[t] % Add the [t] option here to top-align the text on the slide.
\frametitle{Introduction}

\begin{itemize}
\item Academic dishonesty is a serious issue in many developing countries.
\begin{itemize}
\item Cheating in school is a social norm. 
\item Generally, the professors do not take this issue seriously.
\item Low-level of punishment for the perpetrators.
\end{itemize}
\item The objective is to capture a student's decision to either plagiarize or be honest with two prisoner's dilemma models.
\end{itemize}
\end{frame}

\end{document}