The research presented in this volume is the culmination of a two-year process that began in August 2013. That summer, 26 statistics education researchers met in Two Harbors, Minnesota for the Eighth International Research Forum on Statistical Reasoning, Thinking, and Literacy (SRTL-8). The theme for the forum was reasoning about uncertainty in the context of making informal statistical inferences. Over a period of seven days, this group of researchers presented, discussed, and examined research related to the forum’s theme of reasoning about uncertainty in the context of making informal statistical inferences. The research at SRTL-8 covered many different facets (e.g., use of technology and students’ classroom articulation) and explored several different populations of students (primary, secondary, and tertiary levels), adults, and even teachers of statistics. The chapters in this book constitute a subset of that research, and reflect the variation in both the populations and topics studied.