What level of study does data collected from an experimental study where subjects were randomly selected represent?

Data collected from an experimental study where subjects were randomly selected represents Level II evidence in nursing research. This level involves studies that provide evidence from at least one experimental study. The key feature of experimental studies is the random assignment of subjects to either the treatment or control group, which helps minimize bias and allows for a more rigorous examination of the causal relationships between variables.

Level I evidence typically refers to systematic reviews or meta-analyses of randomized controlled trials, which synthesize findings from multiple studies to establish a higher level of certainty regarding the effectiveness of an intervention. Level III evidence usually involves non-experimental studies, such as cohort studies or case-control studies, where there is no random assignment, and Level IV evidence is based on expert opinion or case reports. Therefore, the structure and methodology of a randomized controlled trial align with Level II evidence, making it a crucial component in building effective nursing practices based on scientific research.