Table 5Best study design to answer each type of question

Type of questionBest primary study design
Effectiveness or other impact of in an interventionRCT; other studies that may be considered the absence of RCTs are the following: internally/externally controlled before and after trial, interrupted time-series
Accuracy of information (for example, risk factor, test and prediction rule)Comparing the information against a valid gold standard in a randomised trial or inception cohort study
Rates (of disease, patient experience and rare side effects)Prospective cohort, registry, cross-sectional study
CostsNaturalistic prospective cost study


Cover of Common Mental Health Disorders
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NICE Clinical Guidelines, No. 123.
National Collaborating Centre for Mental Health (UK).
Leicester (UK): British Psychological Society; 2011.
Copyright © 2011, The British Psychological Society & The Royal College of Psychiatrists.

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