Problems with RCT design

Comparing alternative design options for chronic disease prevention interventions

“…Fifth is the concern of imbalance . The validity of a RCT can be compromised when randomization does not balance aetiologic factors between study groups (if aetiology has a substantial impact on outcome) . This potential problem can be addressed by stratification or blocked randomization.…”

“…Observational studies are subject to selection bias, and conventional attempts to correct this type of bias have proved inadequate . Another source of bias in observational studies is insufficient attention to socio‐economic factors .…”

“…When comparing RCTs with observational studies as applied to population‐based prevention interventions, both have strengths and limitations. There has been accumulating criticism about the conduct and reporting of RCTs and substantial attention given to the positive aspects of observational studies . However, the overall quality of the evidence, as assessed in this rapid review, appears uncertain and imprecise and largely could not be assessed for consistency.…”