SYNOPSIS:The process of evidence-based practice (EBP) guides clinicians in the integration of individual clinical expertise, patient values and expectations, and the best available evidence. Becoming proficient with this process takes time and consistent practice, but should ultimately lead to improved patient outcomes. The EBP process entails 5 steps: (1) formulating an appropriate question, (2) performing an efficient literature search, (3) critically appraising the best available evidence, (4) applying the best evidence to clinical practice, and (5) assessing outcomes of care. This second commentary in a 2-part series will review principles relating to steps 3 through 5 of this 5-step model. The purpose of this commentary is to provide a perspective to assist clinicians in interpreting results, applying the evidence to patient care, and evaluating proficiency with EBP skills in studies of interventions for orthopaedic and sports physical therapy. J Orthop Sports Phys Ther 2008;38(8):485-501. doi:10.2519/jospt.2008 describe a number of statistical concepts and procedures commonly used in physical therapy literature. Bandy 6 conducted a 2-year review of the literature published in the journal Physical Therapy and identified 10 statistical procedures that were used in 80% of the articles reviewed. These were descriptive statistics, 1-way analysis of variance (ANOVA), t tests, factorial ANOVA, intraclass correlation, post hoc analyses, Pearson correlation, regression, chi-square, and nonparametric tests analogous to t tests. 6 In this commentary we will review some basic statistical concepts that we feel are important for readers performing critical appraisals. We will also discuss statistical methods used to identify between-group differences in clinical trials that use both continuous scale outcomes and dichotomous scale outcomes, with illustrations from orthopaedic and sports physical therapy literature.
Reporting of Results in Treatment StudiesResults published in studies of physical therapy interventions typically include a summary of the findings from a wide variety of tests and measures that quantify the outcome variables selected by the authors to determine the effects of the intervention being studied. In some instances, such as with case reports or case series, raw data from each subject in the study may be presented. However, this approach is not realistic or warranted in studies with larger samples. More commonly, data are analyzed and reported as aggregated group results. Numerical indices are then used to describe attributes of the aggregated data. The mean or average is a measure that describes central tendency in a distribution of scores, and is most useful for variables that are on an interval or ratio scale. 69 If data exhibit outliers such that the value of the mean would be distorted, the median is often reported as the measure of central tendency. The median might also be preferred over the mean when sample sizes are so small that they may not represent the target population. For example, in...