Up to this point in the text, the functions and time-series samples provided have been created synthetically, chosen to illustrate key theoretical concepts and practical aspects of DFT amplitude-spectrum analysis of discretely sampled time-series signals. This chapter uses DFT tools to analyze real-world data sets and relevant situations. One significant advantage of frequency-domain analysis is its ability to elucidate features of the data that may not be readily apparent by examining the data in the time domain. Explanations of spectral features can promote an ever-deeper understanding of the physical systems that produced the data.