ascertainment bias


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ascertainment bias

systematic failure to represent equally all classes of cases or people supposed to be represented in a sample.

as·cer·tain·ment bi·as

(as-ĕr-tān'mĕnt bī'ăs)
Systematic failure to represent equally all classes of cases or people supposed to be represented in a sample.
References in periodicals archive ?
As such, ascertainment bias, random error, and undercounting cannot be excluded.
"Other studies have found an increased risk of cardiovascular birth defects among depressed mothers not undergoing SSRI treatment, suggesting the possibility of ascertainment bias - worried mothers may pursue more aggressive testing of their infants," says Dr Graf.
Yes, 235 ways scientists can fool themselves, with sober names such as confounding, selection bias, recall bias, reporting bias, ascertainment bias, sex bias, cognitive bias, measurement bias, verification bias, publication bias, observer bias, and on and on.
Characterizing rare mutations in highly selected populations, such as those with very high HDL cholesterol concentrations, may lead to ascertainment bias or chance findings.
"This makes us think this is ascertainment bias," said Valeant consultant Lauren Marangell, MD, a psychiatrist and president of Brain Health Consultants.
Therefore, ascertainment bias is a possibility, despite use of a bilingual staff and consent and donor materials available in Spanish.
First, this study is likely affected by ascertainment bias, because it only reports acute rheumatic fever patients who sought care at the hospital.
Controversy exists with respect to the induction of high-grade cancer by 5ARIs, since both the Prostate Cancer Prevention Trial (PCPT) and the Reduction by Dutasteride of Prostate Cancer Events (REDUCE) trial showed a small increase in Gleason [greater than or equal to]8 in the 5ARI arm.[sup.9,10] Although the FDA published a subsequent warning,[sup.15] investigators believe that the increase reflected ascertainment bias.[sup.16] Prostate cancer mortality from high-grade disease in the PCPT was the same in both groups, suggesting that the increase was artifactual.[sup.17]
The strengths of the study are its large size and varied location of participants from all across the USA and the adjustments for a range of socioeconomic indicators to minimise ascertainment bias.
Ascertainment bias, or decreased genetic variability in species that were not directly targeted in the original marker selection process, is a common finding in genetic studies of microsatellite loci among closely related species (Ellegren et al., 1997: Hutter et al., 1998; Vowles and Amos, 2005).
Ball-park null allele frequencies were estimated from the number of apparent null allele carrying 'parents' and the total number of (non-excluded) parents in the database after correcting for ascertainment bias. In single-child paternity cases, ascertainment bias was compensated for by counting every apparent null allele carrier parent as two null carriers.
Such data are subject to ascertainment bias [15] in which the method of eliciting the suicidal information can result in apparent differences in the rates of these events between treated subjects and untreated controls.