What level of evidence includes quasiexperimental studies?

Quasiexperimental studies are classified as Level 3 evidence due to their design, which lacks random assignment to treatment or control groups, yet still measures the impact of an intervention. This type of research is pertinent in evaluating the effectiveness of interventions when it is impractical or unethical to conduct a randomized controlled trial.

Level 3 evidence is characterized by a moderate level of scientific rigor and includes studies that can offer insights through a variety of observational designs or non-randomized experiments. Such research often assesses outcomes in a natural setting, making it useful for real-world applications, though the risk of bias is greater compared to higher levels of evidence.

Levels 1 and 2 typically encompass more robust methodologies, such as systematic reviews and randomized controlled trials, which offer stronger causal inferences due to their design constraints. Level 5 evidence usually includes expert opinions and anecdotal evidence, representing the lowest level of scientific support. Therefore, recognizing quasiexperimental studies as Level 3 is essential in differentiating the varying strengths of evidence within nursing research.