In the present study secondary school students’ and prospective mathematics teachers’ achievements in probability concepts were investigated. One-way analysis of variance was used to test whether there were significant mean differences among 9th grade, 11th grade and 4th year University Mathematics Education Program students with respect to probability achievement at the 0.05 level. After the analyses, it was found that there were significant mean differences among three groups’ test scores. The Scheffé test was used to find out which group’s mean scores caused the difference. However, statistically significant mean differences were not found between probability achievement mean scores of 11th grade students and prospective mathematics teachers. The means of three groups were low. Also, after the analyses of the questions in the test, it was revealed that most of the students and prospective mathematics teachers do not have probability concepts.

Keywords: Secondary school students, prospective mathematics teachers, probability