Contrary to classical problem-based learning, in guided problem-based learning, the learning goals are predetermined by the instructor--on the basis of a detailed decomposition of the subject matter to be studied--to activate prior knowledge and to structure self-study and subsequent group discussion. This study investigated the effects of classical problem-based learning and guided problem-based learning, for different prior knowledge levels, on perceived value and usefulness of the learning activity and on conceptual understanding of statistics. Participants randomly assigned 110 students to 10 problem-based learning groups, and subsequently, the 10 groups were allocated randomly to classical problem-based learning or guided problem-based learning. The results indicate that guided problem-based learning tends to enhance conceptual understanding of statistics more than break; classical problem-based learning once students have some prior knowledge of the subject. Furthermore, guided problem-based learning tends to increase students' awareness of the value and usefulness of the learning activity.