Step 3 in the Evidence-Based Nursing Practice process is to critically appraise the evidence and then synthesize it to answer your clinical question.
Critical appraisal technique can vary for articles of therapy, diagnosis, harm, prognosis, and systematic reviews. Here are some tutorials will help you learn how to critically appraise research studies.
Chapters 4 and 5 describe how to evaluate the research methods and the appropriate use of statistics in research articles.
Fineout-Overholt E, Melnyk BM, Stillwell SB, & Williamson KM. (2010). Evidence-based practice step by step. Critical appraisal of the evidence: part I: An introduction to gathering, evaluating, and recording the evidence...fifth in a series. AJN American Journal of Nursing, 110(7), 47–52. https://doi.org/10.1097/01.NAJ.0000383935.22721.9c
Fineout-Overholt E, Melnyk BM, Stillwell SB, & Williamson KM. (2010). Evidence-based practice, step by step. Critical appraisal of the evidence: Part II: Digging deeper--examining the “keeper” studies...sixth article in a series [corrected] [published erratum appears in AM J NURS 2010 Nov;110(11):12]. AJN American Journal of Nursing, 110(9), 41–48. https://doi.org/10.1097/01.NAJ.0000388264.49427.f9
The Research Process in Nursing by 
Users' Guides to the Medical Literature: Essentials of Evidence-Based Clinical Practice, Third Edition by See Chapter 7 for randomized controlled trials (RCT)
