Previous research examining comparison relations in word problems primarily focused on students' achievements in word problems with one operation. In this paper, we extend previous research to examine the achievement of students of different ages on word problems that integrate compare and combine word problems, hereafter referred to as…

This study examines how third-graders' conceptions about the origin of species are affected by formal instruction and whether children can learn not only about evolution but also about natural selection. We interviewed the same group of third-grade children (8-9 years old) twice, before and after following a curriculum about these topics.…

We report a study of 10-14 year old children's use of additive strategies while solving ratio and proportion tasks. Rasch methodology was used to develop a diagnostic instrument that reveals children's misconceptions. Two versions of this instrument, one with "models" thought to facilitate proportional reasoning and one without were…