The experiment was done multiple times in two subject areas and with students in grades 4, 5, and 8 Over a 3week period, students were randomly assigned to one of these three groups
Conventional: 30 students in a class are taught the subject matter by a teacher; students are given periodic tests. Mastery Learning: Same as Conventional, but with additional formative assessments and feedback to determine the extent to which students have mastered the topic. Tutoring: Groups of 13 students are taught by a tutor over the 3week period and given the same assessments as the Mastery Learning group. The difference final achievement measures was significant:
The average Mastery student scored higher than 84% of the Conventional students (this is a 1 Sigma or one standard deviation improvement) The average Tutored student scored higher than 98% of the Conventional students (this is the 2 Sigma improvement from the title) 

Science

Technology

Engineering

Mathematics

Empowerment
