Critical thinking skills are the 21st-century life skills that are needed by students. However, in elementary schools, there are no instruments that are truly effective and efficient to measure critical thinking skills. This research aims to develop an open-ended question assessment instrument to measure students' critical-thinking skills, to test…

The study provides evidence concerning elementary school children's ability to conduct a scientific investigation. Two hundred and fifty sixth-grade students and 248 fourth-grade students were administered a test, and based on their performance, they were classified into high-ability and low-ability students. The sample of this study was…