Publisher Summary This chapter discusses best practices and suggestions for analyzing and interpreting user observation evaluation data. The process of analysis is concerned with turning the evaluation data collected into information from which one can make decisions. There are three steps in the analysis of evaluation: collating the data, summarizing the data, and reviewing the data to identify any usability problems. Quantitative data are more eye-catching for the readers of evaluation report and are often regarded as more objective than qualitative data. Reporting is relatively simple if usability metrics are clearly defined. There are three groups of methods for summarizing quantitative data including tabulations, charts, and rankings, descriptive statistics, and inferential statistics such as tests of statistical significance that give the probability that a claim arising from the data can be applied to user population as a whole. On the other hand, quantitative data can reveal the existence of a defect, and perhaps the extent of its impact.