PEDro-P Scale for Critical Appraisal of Group Comparison Studies

10 mins+

The PEDro-P scale

Group comparison research designs include both randomised controlled trials and non-randomised controlled trials. Even if studies use the same research design, they do not necessarily have the same methodological quality.  Methodological quality can be defined as “the likelihood of the trial design to generate unbiased results, that are sufficiently precise and allow application in clinical practice” (Verhagen et al, 2001). Thus critical appraisal of the methodological quality of the study is important to determine how believable the results are and if we should apply them in practice.

The PEDro-P scale is an 11 item rating scale that can be used to determine the external and internal validity of a clinical trial or group comparison study. The scale is used to rate methodological quality of trials for speech pathology on speechBITE and professionals who work with with patients after a brain injury on PsycBITE.

  • Criterion 1 on the scale relates to external validity, and is not counted in the final methodological quality rating score which is out of 10.
  • Criterion 2-9 assess internal validity and address biases prior to the treatment phase (random allocation, concealed allocation and groups being statistically similar at baseline) performance biases during treatment (blinding of participants, therapists and assessors) and biases at data analysis (drop out rates and intention to treat analysis). Criterion 10 and 11 assess the interpretability of the findings by looking at between group statistical comparisons and the reporting of point estimates and measures of variability

The PEDro-P scale was derived from the original PEDro scale. The PEDro scale was developed by a group of researchers from the University of Sydney for use on the PEDro website (Sherrington, Herbert, Maher & Moseley, 2000). The PEDro scale incorporates all 9 items of clinical trial quality identified in the Delphi list developed by Verhagen and colleagues (Verhagen et al, 1998). The PEDro scale contains 2 additional items on the adequacy of follow-up and statistical comparisons between treatment groups.

Both the PEDro-P scale (Murray et al, 2003) and PEDro scale (Maher et al, 2003) have demonstrated reliability. Please see the linked references for more information. 

The only difference between the PEDro-P scale and the original PEDro scale is in the way criterion 4 is defined and applied. The PEDro-P scale was adapted by PsycBITE.

Access and learn to use the PEDro-P scale

For a copy of the PEDro-P scale, please click here.

An online training package is available to help you learn how to use the scale yourself, originally developed by the PsycBITE team.
At this stage, the training utilises either brain injury literature on PsycBITE or speech pathology literature on speechBITE. The fundamentals on how to use the scale to critique articles are still applicable to Optometrists, Ophthamologists and other health professionals.

To access PsycBITE's online training package, please click here.

To access speechBITE's online training package, please click here.



Resource contributed by: Leanne Togher
Affiliation: PsycBITE and speechBITE
Web-site: and
E-mail: leanne.togher[at}
Date uploaded:  23/11/2013
Latest review:  23/11/2013
Reviewed by:  
Next review due:  December 2014

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