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Vol. 23. Issue 4.
Pages 302-310 (01 July 2019)
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Vol. 23. Issue 4.
Pages 302-310 (01 July 2019)
Original Research
DOI: 10.1016/j.bjpt.2018.10.004
Use of 95% confidence intervals in the reporting of between-group differences in randomized controlled trials: analysis of a representative sample of 200 physical therapy trials
Ana Paula Coelho Figueira Freirea,
Corresponding author

Corresponding author at: Department of Physical therapy, Universidade Estadual Paulista Júlio Mesquita Filho, Rua Roberto Simonsen 305, CEP 19060-900, Presidente Prudente, São Paulo, Brazil.
, Mark R. Elkinsb, Ercy Mara Cipulo Ramosa, Anne M. Moseleyc
a Department of Physical Therapy, Universidade Estadual Paulista Júlio Mesquita Filho, Presidente Prudente, SP, Brazil
b Centre for Education & Workforce Development, Sydney Local Health District, Sydney, New South Wales, Australia
c The University of Sydney, School of Public Health, Musculoskeletal Health Sydney, Sydney, New South Wales, Australia

  • Less than one-third of physical therapy trials reported confidence intervals.

  • The prevalence observed is lower than equivalent analyses in other disciplines.

  • Analysis showed consistent increases in the proportion of trials that used confidence intervals with time.

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Tables (2)
Table 1. Summary characteristics extracted from the published reports of the 50 trials randomly selected from 1986, 1996, 2006 and 2016.
Table 2. Mann–Whitney test comparisons between the trials that did and did not report 95% confidence intervals for at least one outcome for three characteristics: number of participants, total PEDro score, and number of primary outcomes identified.
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To assess the prevalence of the use of 95% confidence intervals in the reporting of between-group differences in randomized controlled trials of physical therapy interventions and to determine if the prevalence is changing over time.


Observational study, including an analysis of 200 trials from the Physiotherapy Evidence Database: 50 from each of the years 1986, 1996, 2006, and 2016. The primary outcome used was the prevalence of the between-group difference presented with 95% confidence intervals. We also extracted trial characteristics for descriptive purposes (i.e., number of participants, number of sites involved in recruitment, country(ies) of data collection, funding, subdiscipline of physical therapy, publication language and total Physiotherapy Evidence Database score).


Most commonly, the trials were published in English (89%) and classified in the musculoskeletal subdiscipline (23%). The overall prevalence of use of confidence intervals was 29% and there was a consistent increase in reporting between 1986 and 2016, with peak usage in the 2016 cohort (42%). Confidence intervals were more likely to be used in trials that had received funding, were conducted in Europe and Oceania, and in trials with a Physiotherapy Evidence Database score of at least 6/10.


Most trials of physical therapy interventions do not report confidence intervals around between-group differences. However, use of confidence intervals is increasing steadily, especially among high-quality trials. Physical therapists must understand confidence intervals so that they can understand a growing number of trials in physical therapy.

Confidence interval
Clinical trials as topic
Physical therapy specialty


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