A series of 13 survey questions based on a 50-50 spinner is used to explore school students' understanding of statistical variation in a chance setting. Five questions set the context by assessing understanding of theoretical expectation and representation of repeated trials in a stacked dot (line) plot. Four questions provide opportunity to display appreciation of variation from point expectation and four questions address variation from distributional expectation. A total of 707 students in grades 3 to 9 answered some or all of these questions. A subset of 334 students then took part in a unit of study on chance and data emphasising variation. These students answered a post-test including the same items. Analysis showed a progression across the years of schooling, plateauing at grade 7 and improvement for all grades after instruction. Implications are considered. (Contains 1 figure and 6 tables.) [For complete proceedings, see ED500860.]