Which evidence type is at a lower level than randomized controlled trials?

Randomized controlled trials (RCTs) are considered one of the highest levels of evidence in the hierarchy of research design due to their rigorous methodology that minimizes bias. Quasi-experimental studies, which do not use randomization, are at a lower level than RCTs because they may have higher risks for bias and confounding variables. In quasi-experimental studies, researchers manipulate an independent variable but do not randomly assign participants to treatment or control groups, which can affect the validity of the findings.

Understanding the evidence hierarchy is essential in evidence-based practice, as it informs practitioners about the strength and reliability of the available research. In this context, case reports, although insightful, typically provide weak evidence as they present individual cases without a control group or systematic comparison. Experimental studies can refer to various study designs, but if referring to RCTs, they would not be considered lower than RCTs. Therefore, the correct answer highlights a type of study design that is indeed at a lower level than randomized controlled trials in terms of the quality and reliability of evidence.