��Chapter 7 (Rate Adjustment) Building Concepts Goals To reduce distortions (biases) when making comparisons To encourage  like-to-like comparisons Numerical illustrations of confounding by age Table 7.2 (p. 144) Rates same within age groups but Population B much older Confounding Explanatory factor associated with age Extraneous factor associated with disease Extraneous factor confounds relation between explanatory factor and disease Background  Rate  any incidence or prevalence (economy of language) Crude rate  rate for entire population Strata-specific rate - rate within subgroup Adjusted rate  overall rate compensated for extraneous factor Two methods of adjustment: Direct & Indirect (only direct adjustment was covered) Formula [Keep notation straight; understand the re-compilation of strata-specific rates] Florida & Alaska Example (pp. 146  147) Indirect Age Adjustment [Determine SMR and then adjust rate -- did not cover formula] Adjustment for Multiple Factors We can adjust for multiple factors simultaneously through stratification e.g., 5 age groups, 2 genders, 3 ethnic groups: 5 � 2 � 3 age-gender-ethnic strata Use direct or indirect method of adjustment