title: Occupational Cohort Time Scales.
abstract: OBJECTIVE
  This study explores how highly correlated time variables (occupational cohort time scales) contribute to confounding and ambiguity of interpretation.
  
  
  METHODS
  Occupational cohort time scales were identified and organized through simple equations of three time scales (relational triads) and the connections between these triads (time scale web). The behavior of the time scales was examined when constraints were imposed on variable ranges and interrelationships.
  
  
  RESULTS
  Constraints on a time scale in a triad create high correlations between the other two time scales. These correlations combine with the connections between relational triads to produce association paths. High correlation between time scales leads to ambiguity of interpretation.
  
  
  CONCLUSIONS
  Understanding the properties of occupational cohort time scales, their relational triads, and the time scale web is helpful in understanding the origins of otherwise obscure confounding bias and ambiguity of interpretation.
authors: From Materion Brush Inc. (Dr Deubner), Elmore; and Roth Associates (Dr Roth), Englewood, Ohio.
authors: David C
authors: DC
authors: Deubner
authors: H Daniel
authors: HD
authors: Roth
mesh_terms: D000367:Age Factors; D001608:Beryllium / Q000009:adverse effects; D015331:Cohort Studies; D015986:Confounding Factors, Epidemiologic; D015987:Effect Modifier, Epidemiologic; D006801:Humans; D008175:Lung Neoplasms / Q000139:chemically induced / Q000401:mortality; D009784:Occupational Diseases / Q000453:epidemiology*; D016273:Occupational Exposure; D016272:Occupational Health
chemical_list: D001608:Beryllium
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