Awuah, Francis K.Ogbonnaya, Ugorji Iheanachor2021-07-122021-07-122020-04Awuah, F. K., & Ogbonnaya, U. I. (2020). Grade 12 Students’ Proficiency in Solving Probability Problems Involving Contingency Tables and Tree Diagrams. International Journal of Instruction, 13(2), 819-834. https://doi.org/10.29333/iji.2020.13255a.1694-609X (print)1308-​1470 (online)10.29333/iji.2020.13255ahttp://hdl.handle.net/2263/80765Knowledge of probability is perceived as valuable in the 21st century. This knowledge enables people to understand and make informed decisions relating to uncertain events that occur in real life. Hence, many educational authorities have considered the inclusion of the teaching of probability important in their school curricula. This study investigated Grade 12 students’ proficiency in solving probability problems using contingency tables and tree diagrams as aids. This study employed cross-sectional survey research design, and a mixed method research approach. Data was collected from 342 secondary school students who were conveniently selected from six schools in the KwaZulu-Natal province in South Africa using an achievement test. The study revealed that most of the students (97% and 91%) scored below 50% in solving probability problems involving the use of tree diagrams and contingency tables respectively. The findings show that the students were not proficient in the use of tree diagrams and contingency tables to solve probability problems. The implications of the findings of this study for teacher training and professional development, and textbook publication are discussed and recommendations made.en© 2020, Eskisehir Osmangazi University. International Journal of Instruction is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.Contingency tableMathematicsProbabilityStudents’ proficiencyTree diagramArticle