title: Tutorials in clinical research: part VII. Understanding comparative statistics (contrast)--part A: general concepts of statistical significance.
abstract: OBJECTIVE
  The present tutorial is the seventh in a series of Tutorials in Clinical Research. The specific purpose of the tutorial (Part A) and its sequel (Part B) is to introduce and explain three commonly used statistical tools for assessing contrast in the comparison between two groups.
  
  
  METHODS
  Tutorial.
  
  
  METHODS
  The authors met weekly for 10 months discussing clinical research studies and the applied statistics. The difficulty was not in the material but in the effort to make the report easy to read and as short as possible.
  
  
  RESULTS
  The tutorial is organized into two parts. Part A, which is the present report, focuses on the fundamental concepts of the null hypothesis and comparative statistical significance. The sequel, Part B, discusses the application of three common statistical indexes of contrast, the chi2, Mann-Whitney U, and Student t tests.
  
  
  CONCLUSIONS
  Assessing the validity of medical studies requires a working knowledge of research design and statistics; obtaining this knowledge need not be beyond the ability of the busy surgeon. The authors have tried to construct an accurate, easy-to-read, easy-to-apply, basic introduction to comparing two groups. The long-term goal of the present tutorial and others in the series is to facilitate basic understanding of clinical research, thereby stimulating reading of some of the numerous well-written research design and statistical texts. This knowledge may then be applied to the continuing educational review of the literature and the systematic prospective analysis of individual practices.
authors.affiliation: Department of Otolaryngology--Head and Neck Surgery, Washington University School of Medicine, St. Louis, Missouri 63110, USA. jgneely@aol.com
authors.forename: J Gail
authors.initials: JG
authors.lastname: Neely
authors.forename: James M
authors.initials: JM
authors.lastname: Hartman
authors.forename: James W
authors.initials: JW
authors.lastname: Forsen
authors.forename: Mark S
authors.initials: MS
authors.lastname: Wallace
mesh_terms: D015982:Bias; D002986:Clinical Trials as Topic / Q000706:statistics & numerical data*; D003627:Data Interpretation, Statistical; D006801:Humans; D011336:Probability; D015203:Reproducibility of Results