This study considers students' understanding of a relatively new form of graph in the data-handling curriculum: the stacked dot plot, or as it is more commonly known, the line plot or dot plot. Students in grades 5 to 10 were presented with various forms of a task asking for comparison of two stacked dot plots, one with usual scaling of the base line and the other with gaps for zero-values omitted. Of interest were students' abilities to interpret the information as presented in the graphs, to put the information in context, and to distinguish the statistically appropriate form of graph with an explanation. Performances across grades and forms of the task are compared. For a subset of students in grades 5, 7, and 9 performance is compared for one form of the task before and after a unit of study on chance and data. Discussion includes implications for the classroom in relation to current interest in statistical literacy across the curriculum.