The nurse is researching the use of music therapy for patients with dementia and finds that many research articles have been published about the topic.Which single source will provide the best evidence for the nurse?

A) The opinion of an expert committee
B) Meta-analysis of randomized control trials
C) One well-designed randomized control trial
D) Systematic review of qualitative nursing studies

Systematic reviews or meta-analyses are state-of-the-science summaries from an individual researcher or panel of experts and are on the highest level of the hierarchy.These research summaries are the perfect answers to PICO(T)questions because the researchers have rigorously summarized all current evidence on the question.A single RCT is not as conclusive as a review of several RCTs on the same question.Opinion of an expert committee is on the lowest level of the hierarchy of evidence.Systematic review is above opinions but is below meta-analysis on the hierarchy of evidence.