The purpose of this study was to determine whether there were significant differences in students' performances amongst conceptual, algorithmic and graphical questions tests. Seventy-one eleventh-grade students were involved in this study. In order to assess students' performance, conceptual, graphical and algorithmic questions tests were utilized. Students' performances in each test were analyzed statistically. Statistical analysis using one-way ANOVA of student tests scores pointed to statistically significant differences amongst each of three test scores (P less than 0.05) in favor of the conceptual test. Further analyses were conducted to compare one type of questions with others. From these comparisons, positive relationships were found between conceptual understanding and algorithmic understanding and between conceptual understanding and graphical understanding. Also, results obtained indicated that most of the students lack of graphical understanding. The results suggest that students need more training about graphical understanding.