The results of the testing effect persisted at the end-of-the-year exams 8 months later. This confirms the long-term benefits of retrieval practice. 

Long-Term Benefits of Retrieval Practice (Testing Effect in 6th-Grade class)

Scores on unit exams were a full letter grade higher on material that was quizzed rather than non-quizzed material. Material that was re-exposed as statements of fact scored about the same as non-quizzed material. Therefore, rereading does little help to encode information into long term memory.

University of California, Davis

What if students do better on unit exams merely due to re-exposure to material through the quizzes? To ensure the results are due to retrieval practice, some non-quizzed material was incorporated as statements on the quizzes. Therefore, this extra material would not require retrieval.

Example:
"The Nile River has two major tributaries: the White Nile and the Blue Nile"

Ensuring Results Are Due to Retrieval Practice (Testing Effect in 6th-Grade class)

Brown, Peter C, Henry L Roediger, and Mark A McDaniel. Make It Stick: The Science of Successful Learning. Cambridge, Massachusetts: The Belknap Press of Harvard University Press, 2014. 

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