<P> Systematic reviews are types of literature reviews that collect and critically analyze multiple research studies or papers, using methods that are selected before one or more research questions are formulated, and then finding and analyzing studies that relate to and answer those questions in a structured methodology . They are designed to provide a complete, exhaustive summary of current literature relevant to a research question . Systematic reviews of randomized controlled trials are key in the practice of evidence - based medicine, and a review of existing studies is often quicker and cheaper than embarking on a new study . </P> <P> An understanding of systematic reviews, and how to implement them in practice, is highly recommended for professionals involved in the delivery of health care . Besides health interventions, systematic reviews may examine clinical tests, public health interventions, environmental interventions, social interventions, adverse effects, and economic evaluations . Systematic reviews are not limited to medicine and are quite common in all other sciences where data are collected, published in the literature, and an assessment of methodological quality for a precisely defined subject would be helpful . </P>

From the following descriptions which one best describes a systematic review
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