3. Main data analysis

In the main analysis phase analyses aimed at answering the research question are performed as well as any other relevant analysis needed to write the first draft of the research report.

Exploratory and confirmatory approaches

In the main analysis phase either an exploratory or confirmatory approach can be adopted. Usually the approach is decided before data is collected. In an exploratory analysis no clear hypothesis is stated before analyzing the data, and the data is searched for models that describe the data well. In a confirmatory analysis clear hypotheses about the data are tested.

Stability of results

It is important to obtain some indication about how generalizable the results are. While this is hard to check, one can look at the stability of the results. Are the results reliable and reproducible? There are two main ways of doing this:

Crossvalidation: By splitting the data in multiple parts we can check if analyzes (like a fitted model) based on one part of the data generalize to another part of the data as well.

Sensitivity analysis: A procedure to study the behavior of a system or model when global parameters are (systematically) varied. One way to do this is with bootstrapping (statistics).

Statistical methods

A lot of statistical methods have been used for statistical analyses, e.g. general linear model (usable for assessing the effect of several predictors on one or more continuous dependent variables); generalized linear model (an extension of the general linear model for discrete dependent variables); structural equation modeling (usable for assessing latent structures from measured manifest variables).

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Fundamental science and applied science compared

Fundamental science (or basic science, pure science)is science that describes the most basic objects, forces, relations between them and laws governing them, such that all other phenomena may be in principle derived from them following the logic of scientific reductionism. Physics is a typical fundamental science, chemistry is often included. There is a difference between fundamental science and applied science (or practical science). Fundamental science, in contrast to applied science, is defined as a fundamental knowledge it develops. The progress of fundamental science is based on well controlled experiments and careful observation. Fundamental science is dependent upon deductions from demonstrated truths, or is studied without regard to practical applications. Fundamental science has traditionally been associated with the natural sciences, however, research in the social and behavioral sciences can be deemed fundamental (e.g., cognitive neuroscience, personality).

Experimental physicsregroup all the disciplines of physics that are concerned with data-acquisition, data-acquisition methods, and the detailed conceptualization (beyond simple thought experiments) and realization of laboratory experiments. It is often put in contrast with theoretical physics, which is more concerned with predicting and explaining the physical behavior of nature than the acquisition of knowledge about it.

Although experimental and theoretical physics are concerned with different aspects of nature, they both share the same goal of understanding it and have a symbiotic relation. The former provides data about the universe, which can then be analyzed in order to be understood, while the latter provides explanations for the data and thus offers insight on how to better acquire data and on how to set up experiments. Theoretical physics can also offer insight on what data is needed in order to gain a better understanding of the universe, and on what experiments to devise in order to obtain it.

Experimental physics uses two main methods of experimental research, controlled experiments, and natural experiments. Controlled experiments are often used in laboratories as laboratories can offer a controlled environment. Natural experiments are used, for example, in astrophysics when observing celestial objects where control of the variables in effect is impossible.