One of the key skills you will learn in graduate school is how to work with data: how to collect it, analyze it, and evaluate results.  Data forms the foundation for not only the facts of the political and social world, but also for the value judgements and policy decisions studied by political scientists.  Practically speaking, the most important reason to understand data is to learn how to use it effectively to answer research questions. Watch the following video for a brief introduction to the considerations important to choosing data, measurement, and the methods we use to analyze data.