title: Reduced sensitivity to hidden bias at upper quantiles in observational studies with dilated treatment effects.
abstract: When a treatment has a dilated effect, with larger effects when responses are higher, there can be much less sensitivity to bias at upper quantiles than at lower quantiles; i.e., small, plausible hidden biases might explain the ostensible effect of the treatment for many subjects, and yet only quite large hidden biases could explain the effect on a few subjects having dramatically elevated responses. An example concerning kidney function of cadmium workers is discussed in detail. In that example, the treatment effect is far from additive: It is plausibly zero at the lower quartile of responses to control, and it is large and fairly insensitive to bias at the upper quartile.
authors.affiliation: Department of Statistics, The Wharton School, University of Pennsylvania, Philadelphia 19104-6302, USA. rosenbaum@stat.wharton.upenn.edu
authors.forename: P R
authors.initials: PR
authors.lastname: Rosenbaum
mesh_terms: D015982:Bias; D001699:Biometry; D002104:Cadmium / Q000633:toxicity; D006801:Humans; D007668:Kidney / Q000187:drug effects / Q000503:physiopathology; D015233:Models, Statistical; D016273:Occupational Exposure; D012680:Sensitivity and Specificity
chemical_list: D002104:Cadmium