title: Research methodology and analytic techniques used in the Journal Obstetrics & Gynecology.
abstract: OBJECTIVE
  To quantify trends over time in the research methodology and statistical reporting of published articles in the journal Obstetrics & Gynecology between the years 1991 and 2001.
  
  
  METHODS
  We reviewed 226 articles reporting original clinical research in Obstetrics & Gynecology, including 75 consecutive articles from 1991 and 1996 and 76 consecutive studies from 2001. Articles were classified by research methodology and level of evidence: I for randomized trials; II for controlled trials and observational, analytic studies; and III for case reports or case series. We also noted whether the investigators reported a research hypothesis, P values, effect sizes, 95% confidence intervals, and sample size/power calculations. We calculated chi2 for linear trend to evaluate changes over this 10-year period.
  
  
  RESULTS
  Seventy-four percent of the 226 studies evaluated were level II. The percentage of randomized trials did not increase from 1991 to 2001. However, level II studies increased from 71% in 1991 to 88% in 2001 (P = .01). During the same period, level III studies (case reports and case series) declined from 19% in 1991 to 1% in 2001 (P < .001). We also noted that a clearly stated research hypothesis, effect measures (and respective confidence intervals), and sample size calculations were more common in more recent years.
  
  
  CONCLUSIONS
  In the journal Obstetrics & Gynecology, we noted that observational, analytic studies increased in frequency, anecdotal reports decreased, and statistical reporting has improved. However, there still exists considerable opportunities for improvement.
authors.affiliation: Division of Research and the George Anderson Outcomes Measurement Unit, Department of Obstetrics and Gynecology, Women & Infants Hospital, Brown Medical School, Providence, Rhode Island 02905, USA.
authors.forename: Lindsay
authors.initials: L
authors.lastname: Dauphinee
authors.forename: Jeffrey F
authors.initials: JF
authors.lastname: Peipert
authors.forename: Maureen
authors.initials: M
authors.lastname: Phipps
authors.forename: Sherry
authors.initials: S
authors.lastname: Weitzen
mesh_terms: D002986:Clinical Trials as Topic; D016021:Epidemiologic Studies; D005260:Female; D006176:Gynecology; D006801:Humans; D009774:Obstetrics; D010506:Periodicals as Topic / Q000639:trends*; D011786:Quality Control; D012107:Research Design / Q000639:trends*; D013223:Statistics as Topic / Q000639:trends*