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Sample Size Requirements in Studies of the Etiologic Fraction
Author(s) -
Smith Judith A.,
McHugh R. B.
Publication year - 1988
Publication title -
biometrical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.108
H-Index - 63
eISSN - 1521-4036
pISSN - 0323-3847
DOI - 10.1002/bimj.4710300211
Subject(s) - statistics , sample size determination , fraction (chemistry) , estimator , attributable risk , mathematics , population , sample (material) , demography , econometrics , medicine , environmental health , chemistry , organic chemistry , chromatography , sociology
This paper outlines methods of determining sample size for epidemiologic research in studies of the etiologic fraction. The basic model with a dichotomous disease and a single dichotomous exposure factor is considered. To determine sample size, the researcher must specify: the magnitude of the etiologic fraction ε to be detected as statistically significant, the level of significance α, the power 1 ‐ β of the test, p the proportion of the population exposed to the risk factor and R the proportion of the population with the disease. Sample size formulas and tables are presented for the case‐control, cohort and cross‐sectional designs. Optimal allocation considerations are examined to minimize cost for a specified power. Extensive use is made of Walter's results concerning the asymptotic variance of the maximum likelihood estimator of the etiologic fraction for the three epidemiologic study designs.