Evidence-Based Practice Tutorial #4 Identifying the Magnitude of the Effect Part 2 Number Needed to Treat (NNT) represents an estimate of the number of subjects that need to be treated to achieve a single positive outcome. The advantages of the NNT metric include its consideration of individual data and its relative transparency (i.e., it is easy to interpret). There is more than ... Tutorial
Tutorial  |   April 01, 2003
Evidence-Based Practice Tutorial #4 Identifying the Magnitude of the Effect Part 2
Author Affiliations & Notes
  • Patricia Hargrove
    Department of Speech, Hearing, and Rehabilitation Services, Minnesota State University, Mankato, MN
Article Information
Research Issues, Methods & Evidence-Based Practice / Evidence-Based Practice Tutorial
Tutorial   |   April 01, 2003
Evidence-Based Practice Tutorial #4 Identifying the Magnitude of the Effect Part 2
SIG 1 Perspectives on Language Learning and Education, April 2003, Vol. 10, 30-31. doi:10.1044/lle10.1.30
SIG 1 Perspectives on Language Learning and Education, April 2003, Vol. 10, 30-31. doi:10.1044/lle10.1.30
Number Needed to Treat (NNT) represents an estimate of the number of subjects that need to be treated to achieve a single positive outcome. The advantages of the NNT metric include its consideration of individual data and its relative transparency (i.e., it is easy to interpret).
There is more than one way to calculate NNT. The strategy presented here was presented in Yampolsky and Matthies (2002)  and involves (a) defining a successful treatment outcome if it is not already defined in the existing data; (b) classifying each treatment and control subject as improved or not improved; (c) calculating the magnitude of the treatment effect using a set of NNT formulae (Table 1).
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