Deciding how to analyze data involves many choices. Researchers choose from an array of analytical tools and statistics. The selection is based on a knowledge of specific tools and statistics, the questions the research is to answer, and the properties of the variables, data and the sample. Investigators identify certain tools as appropriate for typical questions and data in their professions. Consequently, planners, psychologists, engineers, financial analysts, and administrators may prefer different approaches to analysis and work with different statistics. In carrying out management and policy-making tasks, public administrators rely on analytic approaches favored by social scientists. They use the tools of sociologists and political scientists in working with cross-sectional data, the tools of economists and statisticians in working with time series, and the tools of psychologists in working with experimental and quasi-experimental designs.