An empirical effort or process is one which is data-based. The fundamental difference between scientific research and other methods of inquiry is that scientific research is data-based. A fundamental tenet of the scientific method is that an outcome or result is not regarded as valid until there is a substantial body of hard evidence or data to support it. Another way to say this is that empirical studies are ones which make use of hypothesis testing or reality-testing to determine whether assertions, hypotheses, or theoretical frameworks will be regarded as valid. Exploratory data analysis can be thought of as preliminary to more in depth statistical data analysis.
Box plots are a primary tool in exploratory data analysis.
The family of Gaussian or normal distributions is a category of frequency distributions fitting a precise mathematical model. When plotted on a graph, they are characterized by continuous, symmetrical, bell-shaped curves. These curves represent the mathematical law of errors. The curves precisely describe the phenomenon that measurements often include small errors, and that as errors become larger they decrease in number. Gaussian distributions are important to the clinician because they represent many situations where a condition is the result of a variety of factors summing together.