High school mathematics teachers’ reading of tables

People frequently do not use numeric information as providers intended. Some lapses arise from psychological issues, but more errors (even among educated professionals) come from lack of mathematical skill. Lack of training is a cause; for instance, finding probabilities from tables appears in current US school standards, but not many earlier versions. To investigate teacher knowledge, 25 US high school mathematics teachers were interviewed on tasks related to tables and conditional probability. Although participants made mistakes, their content knowledge compared favorably to the general population. Interviewed teachers recognized common misconceptions and could offer potential suggestions to help students, but teachers acknowledged their lack of experience on the subject. Discussion includes how curriculum choices might develop students’ knowledge of categorical variables.