ABSTRACT
This chapter analyses the result of the measurement of a given variable as a function of various physical parameters as data. In any case, the Fourier Transform is obviously the tool to be used for any analysis and further processing of deterministic data. Random variables are quite different. Processing is the act of transforming the data, and rejecting part of the content in order to keep only what one defines as ‘useful’. There is a very simple means of estimating quantitatively both the information conveyed by a data set and the information changes due to any kind of data processing. The ultimate goal of data processing is to split the ‘useful signal’ from the background and the noise. Since the treatment of the background can be done by deterministic equations, the first step of analysis is of course the evaluation of the so-called signal to noise ratio which can be seen as a kind of ‘quality factor’ of the measurement.
