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J Am Coll Radiol. 2016 Aug;13(8):979-84. doi: 10.1016/j.jacr.2016.03.031. Epub 2016 May 26.

Effect of Massed Versus Interleaved Teaching Method on Performance of Students in Radiology.

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Columbia University Medical Center, New York, New York.
Columbia University College of Physicians and Surgeons, New York, New York. Electronic address:
Columbia University College of Physicians and Surgeons, New York, New York.
Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, Connecticut.



Radiology instruction is based on the principle that grouped (or massed) repetition of an intellectual activity leads to expertise. The aim of this study was to test the hypothesis that the spaced (or interleaved) method of teaching chest x-ray interpretation is more effective than the massed method.


After institutional review board approval was obtained, 40 first- and second-year medical students were randomized into two groups matched by age, gender, and education experience. Both groups saw six examples of 12 common chest radiographic patterns, one grouped, the other scrambled randomly without repeating strings. After a distraction, participants took a multiple-choice test consisting of two cases in each radiographic pattern, one previously shown, one new. Results were analyzed using two-tailed Student's t test of proportion.


Comparing interleaved and massed groups, the average overall score was 57% versus 43% (P = .03), the recollection score was 61% versus 47% (P = .03), and the induction score was 53% versus 40% (P = 0.10), respectively. Comparing second- and first-year students, average scores were 67% and 39%, respectively (P < .01). First-year students in the interleaved and massed groups scored 55% and 36% (P = .02) in recall and 40% and 28% (P = .10) in induction. Second-year students in the interleaved and massed groups scored 71% and 63% (P = .36) in recall and 74% and 59% (P = .03) in induction.


The interleaved method of instruction leads to better results than the massed method across all levels of education. A higher level of medical education improves performance independent of method of instruction.


Medical student education; chest plain film; teaching method

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