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Evidence Hierarchies refer to the ranking of research studies based on the strength and reliability of their findings. In evidence-based nursing and healthcare, higher levels of evidence come from studies that minimize bias and provide stronger support for clinical decision-making.
A simplified hierarchy (from strongest to weakest evidence) is:
Systematic Reviews & Meta-Analyses – Combine results from multiple high-quality studies (often RCTs) to give the most reliable conclusions.
Randomized Controlled Trials (RCTs) – Participants are randomly assigned to intervention or control groups; considered the gold standard for testing interventions.
Cohort Studies – Follow groups over time to examine relationships between exposures and outcomes.
Case-Control Studies – Compare people with a condition to those without to find possible causes or risk factors.
Cross-Sectional & Descriptive Studies – Provide a snapshot of a population or phenomenon at one point in time.
Qualitative Studies – Explore experiences, perceptions, or processes to understand why and how phenomena occur.
Expert Opinion / Background Information – Based on clinical expertise or non-research sources; valuable but least strong in terms of scientific evidence.
By Carrie Price | Towson University Library