Recall and observation bias was probable in the Interphone study since interviews were computer based and conducted at the subject's home, the hospital or another place.
Lastly, recall bias is likely for established or probable risk factors of lung cancer, such as smoking and air pollution, in a case control study.
However, these previous studies are likely to be subject to the same influence of selection bias and it is probable that older women unable to consent/take part in an interview would have poorer health than younger ones who can.
However, the study was not restricted to patients on mechanical ventilation, which may induce bias, because it is probable that patients not on mechanical ventilation are likely to have a less severe TBI and hyperoxemia is more likely with mechanical ventilation [ 44].
Cloning bias is the probable cause of this deviation from expectation.
Thus, exclusion of these individuals was not linked to the exposure and consequently, the risk of selection bias is less probable.
However, this bias is less probable in our study, since we included guidelines from several countries, differing in funding and reimbursement [ 97, 98], availability and accessibility [ 99, 100] of healthcare.
We also wish to emphasize that verification bias is also probable if it is some other test (not the test under evaluation) that influences the clinician's decision to recommend the gold standard (depending on the correlation between the other test and the test being studied).
Diary responses are not subject to recall bias (assuming prospective completion) hence it is probable that the diary information provides the more accurate figure, compared with the CATI.
This is probable non-differential misclassification, and will bias the results towards the null hypothesis.
