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Bloom's 2 Sigma Problem, explained for parents
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Bloom's 2 Sigma Problem comes from educational psychologist Benjamin Bloom's 1984 finding that students taught one-to-one with mastery learning performed about two standard deviations (2 sigma) better than students taught in a conventional class — the average tutored student outperformed about 98% of the classroom group. The 'problem' is that personal tutoring for every child is too expensive. Bloom the app is named after it and tries to bring the key ingredients of tutoring to every child.
What makes tutoring work
Research on Bloom's findings points to a few ingredients: material at the right level for the individual, immediate correction of mistakes, frequent practice with feedback, and moving on only once a concept is mastered.
How the app applies it
Every wrong answer is corrected immediately with a short explanation. Difficulty targets roughly 85% success. Concept memory tracks what each child has mastered so the next game builds on it. Praise names the strategy the child used, which research links to persistence.
What it doesn't claim
An app is not a human tutor, and no study has measured a 2 sigma effect for Bloom. The name is a goal: getting as close as possible to what one-to-one tutoring does, for every child, from one photo.