This chapter will discuss standard and advanced data-collection techniques in X-ray absorption spectroscopy and the determination of precision, accuracy and uncertainty using such approaches. In general, any independent measures of precision and accuracy should be expected from data collection and pre-analysis, and any conclusions drawn from the data should be based upon them. Hence, fitting, modelling and local or nanostructural determination should be based upon independent uncertainties, however developed and even if some measures or systematics are unavailable. The key difference in application between processing without uncertainty or precision and processing using independent estimates of precision or uncertainty is between a fingerprinting approach or confirmation of the possibility of a proposed structure (without uncertainty) and a quantitative hypothesis testing to lead to structural information and determination. Since this chapter is intended to be short, it will point towards discussions in other parts of this volume and to some key literature discussions.