The Evidence on Teaching

Blocking vs. Interleaving: Single-Session Effects Within Middle School Math Homework

Ostrow, K., Heffernan, N. T., Heffernan, C., & Peterson, Z. · 2015

grade Crctindependentfailed
Sample
Middle-school students, online homework
Population
Middle-school students; single-session online math homework; short delay (~2-5 days).
Design
Classroom RCT inside the ASSISTments platform. Brief single-session dosage — the regime where blocking can match interleaving.
Key findings
A classroom RCT that did NOT find an interleaving benefit — a brief single-session manipulation with short delay, the regime where blocking matches interleaving. Tempers 'interleaving always wins'; the effect is conditional on delay and dosage.
Genetic confound
Domain-skill outcome.
Replication notes
The one prior math study finding no positive interleaving effect (Rohrer 2020 attributes it to short delay).
DOI / URL
10.1007/978-3-319-19773-9_34

Effects

OutcomeMetricValueMeasureTimingVsHorizonClass
Interleaved vs blocked, short-delay testdirectionNULL — no interleaving benefitresearcher-designedimmediate/short; classroomactive-alternativeend-of-treatmentdomain-skill
Low-skill studentsdirectionsome benefit on learning gains / reduced hintsresearcher-designedimmediateactive-alternativeend-of-treatmentdomain-skill

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Blocking vs. Interleaving: Single-Session Effects Within Middle School Math Homework · The Evidence on Teaching