Comment 1: Control of extraneous variables is essential in research studies to ensure accurate understanding of the relationships among variables. Extraneous variables refer to any other factors that may influence the outcomes of the study, apart from the variables of interest. In the example given, the focus is on the effect of relaxation therapy on the perception of incisional pain. To control extraneous variables, the researchers need to consider factors such as the type of surgical incision, the amount, time, and type of pain medication administered after surgery. By selecting only patients with abdominal incisions who are hospitalized and receiving a specific type of pain medication intravenously after surgery, the researchers can control some of these extraneous variables. Controlling extraneous variables allows researchers to accurately determine the effects of the intervention or treatment on the study outcomes.
Comment 2: The levels of evidence in research studies can be categorized from strongest to weakest. The strongest level of evidence is a systematic review of well-designed randomized controlled trials (RCTs). This involves evaluating multiple RCTs in a specific area of research. Meta-analyses of experimental and quasi-experimental studies are also considered strong evidence, as they use quantitative approaches to review research findings from multiple studies. Integrative reviews of experimental and quasi-experimental studies involve compiling and summarizing relevant research. Single experimental studies, which are true experimental studies where researchers are typically unaware of who is receiving the intervention, are another level of evidence.
Moving down the hierarchy, meta-analyses of correlational studies, integrative reviews of correlational and descriptive studies, qualitative research meta-synthesis, meta-summaries, single correlational studies, and single qualitative or descriptive studies are considered weaker levels of evidence. Opinions of respected authorities based on clinical evidence or reports of expert committees are also included in this hierarchy.
Systematic reviews are reviewed by experts in the field who meticulously evaluate the content, ensuring high quality and reliability. Meta-analyses compile quantitative data from multiple studies, searching for common themes and trends. Integrative reviews compile and abridge research findings, providing a comprehensive overview. Single experimental studies involve rigorous experimental designs, increasing internal validity.
In conclusion, controlling extraneous variables is crucial in research studies to obtain accurate results. The hierarchy of evidence helps researchers determine the strength of different types of studies and the reliability of their findings. Systematic reviews, meta-analyses, and integrative reviews are considered strong levels of evidence, while single experimental studies and meta-analyses of correlational studies are weaker forms of evidence. Understanding these levels of evidence aids in conducting rigorous research and making informed decisions.
