Bloom's 2 sigma problem

The phenomenon's associated problem, as described by Bloom, was to "find methods of group instruction as effective as one-to-one tutoring". The phenomenon has also been used to illustrate that factors outside of a teachers' control influences student education outcomes, motivating research in alternative teaching methods, in some cases reporting larger standard deviation improvements than those predicted by the phenomenon. The phenomenon has also motivated developments in human-computer interaction for education, including cognitive tutors and learning management systems.

Mastery learning

Mastery learning is an educational philosophy first proposed by Bloom in 1968 based on the premise that students must achieve a level of mastery (e.g., 90% on a knowledge test) in prerequisite knowledge before moving forward to learn subsequent information on a topic. Mastery is determined with regular tests, and students who do not yet achieve mastery on the test are given additional educational support before another test. This cycle continues until the learner accomplishes mastery, and they may then move on to the next stage. Failure for a student to achieve mastery is viewed, differently from conventional educational testing, as due to instruction rather than lack of student ability. Another key element of mastery learning is that it requires attention to individual students as opposed to assessing group performance. There is good evidence to suggest the effectiveness of mastery learning for improving student educational outcomes.

Two of the three groups in the original study by Bloom conducted mastery learning, with one control group that did not.