Student Achievement and Bloom’s 2 Sigma Problem

By Janet Pinto, Chief Academic Officer, Curriki

In 1984 Benjamin Bloom, an American educational psychologist and professor at the University of Chicago, published “The 2 Sigma Problem: The Search for Methods of Group Instruction as Effective as One-to-One Tutoring” in the academic journal Educational Researcher. His research demonstrated a very large positive effect on learning via one-on-one tutoring using his mastery learning methodology, when compared to classroom instruction. His results demonstrated 2 standard deviations (2 sigma) of statistical significance advantage to students from tutoring with mastery learning methods.

That is, randomly chosen students who were tutored on average performed 2 standard deviations better than the students in a conventional classroom. This means the average tutored student was performing above 98% of the conventional classroom students!

He next considered what could be done in non-tutorial, group settings – in the classroom – to improve learning. Bloom and his graduate students considered and tested various combinations of variables, focusing only on those variables that individually had a 0.5 or higher effect size (standard deviation, essentially).

A mastery learning (feedback-corrective) methodology provided 1 standard deviation improvement in performance, which corresponds to the average student under this methodology outperforming 84% of traditional classroom students.

Mastery learning can occur in a classroom setting, but invokes more feedback and corrective procedures in the learning process. Feedback is frequent and specific and students are evaluated relative to the material, not in comparison to one another. The material to be mastered is broken down into small discrete lessons, each of which must be sufficiently mastered in turn before moving on to the next lesson. A summary can be found in this Wikipedia article:

The digital learning revolution, with its flipped classroom concepts and more individualized learning style, is actually closely related to mastery learning, as discussed in this blog and video:

“They have to do 75 percent or better,” say chemistry teacher Jonathan Bergmann. “If they don’t, they go back until they get it…If I’ve got a kid who is a rocket scientist, I can challenge him…every kid gets a different education.”

Curriki, as an open source repository for curricular materials, is a resource that is very well suited to support the mastery learning methodology. Curriki contains a wide range of materials, covering a full set of K12 subjects, and that can be adapted to the requirements of various students.

From Bloom’s 1984 paper, which can be accessed from the Wikipedia article on the 2 sigma problem:

One response to “Student Achievement and Bloom’s 2 Sigma Problem

  1. Excellent article. For the University level, is COURSERA the solution to The 2 Sigma Problema?
    (See TED TALKS Daphny Koller “What we’re learning from online education”)

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