Tadayoshi Kaya

Abstract This entry explores three fundamental aspects of data analysis in applied linguistics: descriptive statistics, data display, and data transformation. First, it delves into descriptive statistics, highlighting its use in the interpretation and summarization of data. Then, it concentrates on measures of central tendency—mean, median, and mode—and their ability to reveal typical data behaviors. It also elaborates on measures of dispersion, such as the range, interquartile range, and standard deviation, underscoring the necessity to account for data spread alongside central values. Second, the entry explores the significance of data visualization in comprehension and comparison of data, reviewing various display methods, including pie charts, bar charts, histograms, line charts, stem‐and‐leaf plots, and box plots. Finally, the entry culminates with a discussion on data transformation. It shows how data transformation is used to meet the assumptions of parametric tests and normalize the shape of distributions. It also briefly mentions logarithmic transformation and other related techniques. In addition, it introduces the concept of standard scores, including z ‐scores and T ‐scores, emphasizing their utility in comparing data on a unified scale.