3: Basic concepts of statistical reasoning: Standard errors and confidence intervals

statistical analysis or statistical inference, to be distinguished from the descriptive statistical analysis that is involved in obtaining tables of frequencies, scatterplots of data and so on, as described in the previous article of this series.1 This discussion requires an understanding of a number of basic statistical concepts and terms, key among them being the idea of sampling variability. To explain the fundamental role of this concept we need to introduce the notions of population and sample and probability. We will then explain how the concept is used in the form of standard errors and confidence intervals.