If the randomization procedure causes an imbalance in covariates related to the outcome across groups, estimates of effect may be biased if not adjusted for the covariates which may be unmeasured and therefore impossible to adjust for. For one, it has been argued that equipoise itself is insufficient to justify RCTs. For example, interventions can inadvertently induce socioeconomic and behavioral changes that can confound the relationships Bhargava, The questionnaire battery was the same at baseline and at short term; long term assessment included two additional scales measuring functional status 56 and impact of illness 57 not reported here. Participants attended the tai chi training sessions more often than participants attended aerobic exercise. The information was, however, seldom reflected in the meta-analyses. Aerobic exercise sessions were 60 minutes, twice a week, for 24 weeks. Setting Urban tertiary care academic hospital in the United States between March and September At short term assessment, the survey battery was primarily administered as a postal survey with one reminder letter for non-responders; some participants also received telephone reminders.
The study statistician CHS generated random sequences in the R statistical package, blocking on instructor within the tai chi group and unblocked within the aerobic exercise group. Using a two sided hypothesis test at 0. Putative benefits for patients included a better understanding of their condition and how to look after themselves through the development of self care behaviours and the continued support of services such as community matrons web appendix 1. Causes of similarity within practices include pre-existing case mix differences between practice populations, and both general and specific practice effects for example, factors that facilitate or inhibit access, general practitioner case load, the extent to which care is centred around the patient. To account for practice differences, multilevel modelling was used with observations at different time points nested within participants, and participants nested within practices. We intend to disseminate the main results to trial participants and will pursue patient and public involvement in the development of an appropriate method of dissemination. We also provided printed materials on exercise principles, practicing techniques, and safety precautions, and explained exercise theory and procedures for fibromyalgia. Main outcome measures The primary outcome was change in the revised fibromyalgia impact questionnaire FIQR scores at 24 weeks compared with baseline. This may occur when covariates that affect the outcome are not equally distributed between treatment groups, and the treatment effect is confounded with the effect of the covariates i. We used longitudinal fixed effects models based on the intent-to-treat principle to determine the comparative efficacy of the five treatments at baseline and at 12, 24, and 52 weeks. Tai chi Before study initiation, we developed a standardized classic Yang style tai chi protocol for fibromyalgia based on the literature. All analyses reported here exceed the required sample size and are therefore adequately powered. The first study compared an aerobic and flexibility exercise program with education and detected a mean improvement of 7. We conducted several sensitivity analyses, including multiple imputation and adjustment for attendance rate and variables that were found to differ among participants who missed visits. If the randomization procedure causes an imbalance in covariates related to the outcome across groups, estimates of effect may be biased if not adjusted for the covariates which may be unmeasured and therefore impossible to adjust for. Results Between March and September we screened potential participants by telephone. Here, data in the results section are taken from the primary analyses unless specified as being from secondary analyses. While RCTs can be useful in policy evaluation, it is necessary to exercise care in interpreting the results in social science settings. Non-random "systematic" methods of group assignment, such as alternating subjects between one group and the other, can cause "limitless contamination possibilities" and can cause a breach of allocation concealment. First is choosing a randomization procedure to generate an unpredictable sequence of allocations; this may be a simple random assignment of patients to any of the groups at equal probabilities, may be "restricted", or may be "adaptive. Repeated measures for each outcome over the trial period were analysed with the linear mixed model procedures in SPSS. Patients had pre-established, tailored care plans that included routine assessments at a frequency appropriate for their disease severity—typically ranging from once per week to once or twice per year. Traditionally, blinded RCTs have been classified as "single-blind", "double-blind", or "triple-blind"; however, in and two studies showed that these terms have different meanings for different people. No serious adverse events related to the interventions were reported. We repeated analyses on each of the ten imputed datasets, and thereafter used standard multiple imputation procedures to combine the multiple scalar and multivariate estimates 75 76 77 with SPSS version 19 and NORM. Outcome measures We assessed key clinical outcomes focused on symptom severity and body pain drawn from previous randomized trials, exercise literature, and recommendations by the American College of Rheumatology.
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