Bias in observational studies.
Swedish National Competence Center, Musculoskeletal Disorders (NKO),Klinikgatan 22, Lund University Hospital,SE-22185 Lund, Sweden. jr@nko.se
Jonas
J
Ranstam
D015982:Bias; D015986:Confounding Factors, Epidemiologic; D006801:Humans; D019370:Observation; D013223:Statistics as Topic