Understanding the research methodology: should we trust the researchers' conclusions?

Understanding the methodology section of research articles is difficult for those unfamiliar with research design, but is essential for judging the credibility of the researchers' findings. The methodology section describes measures taken to avoid reaching the wrong conclusions. When comparing two or more treatments, researchers might find a difference in treatments when none exists (type I error) or not find a difference when there actually is one (type II error). Type I errors are minimized by random assignment to treatment and control groups, double blinding, ensuring that the treatment under study is the only difference between groups, and setting the level of significance in advance. Type II errors are minimized by using an adequately sized, homogenous sample, increasing the treatment strength, measuring precisely, and using appropriate statistics. The purpose of this article is to explain these common experimental strategies and statistical terms.