The use of dual or multiple reports in epidemiologic studies.

Weak measurement of epidemiologic exposures is an impediment to appreciation of the effects of those exposures. This paper discusses two strategies to assess the true effects of weakly measured exposure. The first is to use external information about the extent of mismeasurement to adjust estimates of the effects of exposure. The second strategy is to use multiple measurement--to repeat the measurement in such a way that measurement errors are not repeated. The major disadvantage of the adjustment strategy is its sensitivity to incorrect specification of mismeasurement structure. The primary disadvantage of the multiple measurement strategy is its inefficiency. Unless epidemiologists are quite confident, about the extent and structure of measurement error in their data, they should rely primarily on multiple measurement, and secondarily on adjustment procedures.