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Main Effects-- Internal Analysis

For the internal analyses the ERR maineffects model is expressed as

where is the observed cancer death rate per thousand person years at risk in the cell. In this specification all of the terms are factors (one parameter for each level) except for age and dose, and birth cohort is the ``referent factor''. The baseline rates are described by the first six estimates in column 2 of Table AV , e.g. for the 1915 birth cohort the estimated baseline rates are log (rate) = 0.728 + 5.20 * log (age/52.5). Consequently, the estimates for the factor B in column two (lines 2 through 6) of Table AV represent the log of the all cancer mortality rate for each of the five birth cohorts at the reference age 52.5 (i.e. they are the intercept parameters). The estimates for each level of the factors S, L, IG, and F are relative risks (in L% units), with the first level of each factor as the referent category. The next to last estimate in column two is the estimated dose-response coefficient for external radiation dose and represents the change in the ERR per Sv, which is equivalent to percent per 10 mSv (rem). Estimates of the standard errors of each of the parameter estimates are given in column 3 of Table AV , and likelihood ratio based 95% CI are given for the ERR in the last row. The 95 percent confidence intervals were obtained using the bounds command in an AMFIT program (AMFIT is part of epicure[11])