Access Type

Open Access Dissertation

Date of Award

January 2019

Degree Type


Degree Name



Education Evaluation and Research

First Advisor

Shlomo S. Sawilowsky


Evidence-based practice requires physical therapists to make clinical decisions about the best intervention to use when providing services to patients/clients. Although null hypothesis significance testing (NHST) is frequently used to interpret the outcome of a clinical trial investigating the comparative effectiveness of an intervention, statistical significance does not directly translate into clinical importance. Number needed to treat (NNT) is a measure of effect size (ES) that may be particularly useful when translating the results from clinical trials to PT clinical practice. The purpose of this study was to conduct a bibliometric content analysis of the methods of reporting research results of clinical trials published in the physical therapy specific literature, specifically NHST, ES and NNT.

The frequency of reporting the result of NHST, EST and NNT was examined in 448 clinical trials published in three physical therapy specific journals (Journal of Neurologic Physical Therapy, Journal of Orthopaedic Physical Therapy and Physical Therapy) between 1989 and 2018. More than 90% of clinical trials included a report of the result of NHST but less than 30% reported effect size. NNT was only eight (1.79%) articles. The number of articles in which NNT was reported during 2013-2018 was statistically greater than the previous four 5-year periods. However, there was no positive linear trend of the frequency of NNT during the last nine years, 2010 – 2018. This is the first study in which evidence is presented indicating increased reporting of NNT in the physical therapy specific literature however there is no evidence of a positive trend during the past nine years. Physical therapist students, educators, researchers and practitioners would be well served to improve their understanding of how to include NNT in clinical trial research designs to improve decisions about the clinical importance of an intervention.