Define ascertainment. ascertainment synonyms, ascertainment pronunciation, ascertainment translation, English dictionary definition of ascertainment. tr.v. as·cer·tained , as·cer·tain·ing , as·cer·tains 1. To discover with certainty, as through ex
Medical sources sometimes refer to samppng bias as "' ascertainment bias " '.Ascertainment bias has basically the same definition, but is still sometimes classified as a separate type of bias.Some regard these studies as exhibiting ascertainment bias which created an impression that...
In this manuscript, we present ways to estimate the ascertainment bias for a time-to-event outcome, and discuss its impact on the overall power of a trial versus changing of the outcome definition to a more stringent unbiased definition that restricts attention to measurements less subject to ...
Osteoporosis is most commonly classified using the World Health Organization (WHO) operational definition and based on aBMD measurement using dual X-ray absorptiometry (DXA), relative to the aBMD of an average young adult [14,15,16]. Using this approach, osteoporosis patients are those with an a...
In this paper, I show that, for a fictitious disease that is strictly nongenetic and nonenvironmental, lambdaS can be dramatically inflated because of misunderstanding of the original definition of lambdaS, ascertainment bias, and overreporting. Therefore, for a disease of entirely environmental origin...
In this article, we present ways to estimate the ascertainment bias for a time‐to‐event outcome, and discuss its impact on the overall power of a trial vs changing of the outcome definition to a more stringent unbiased definition that restricts attention to measurements less subject to ...
The conclusion that the incidence of gastro-oesophageal reflux disease (GERD) was higher in patients with depression than in those without should be interpreted with caution because of ascertainment bias and an imprecise definition of GERD. Although depression could hypothetically increase the incidence ...
This bias can affect any observational study wherein case definition depends on diagnosis times (e.g., health-plan enrollment data). To avoid bias in observational investigations of cancer screening wherein the case definition depends on the diagnosis date, one must ensure that both screening and...