One-group pretest-posttest design was used in this study. It was determined to measure the effect of sample
lesson plan on student’s achievement level. The study was conducted in the fall semester of the 2013-2014 academic
year. The participants were 12 eight-grade students (four boys and 8 girls). In teaching the subject to the students,
the sample lesson plan based on STEM approach was used in compliance with 5E learning cycle model.