Data selection biases

Images of diffuse emission are more sensitive to large-scale uncertainties in the background model, data selection biases, or systematic effects of the imaging methods. 

Fig. 5 All data-point conductance histograms (upper panel) of gold atomic contacts formed at various electrode potentials in 0.1 M H2S04 solution. The histograms were built from 1,000 single curves without data selection. The corresponding plateau distributions are plotted in the lower panel. All measurements were carried out with a bias voltage of 0.10 V. The tip moving rate was 60 nm s-1...

As discussed by Hood and Miller (7), and in the lecture by Hood at the Maternal Toxicology Symposiums in 2009 (summarized in Beyer et al. (8)), it can be argued that it is Khera s interpretation, rather than the developmental toxicity study results themselves, that may be of concern. Khera s literature review indicated a possible association between maternal toxicity and embryo-fetal effects, but it did not establish a causal relationship between these two observations. Additional criticisms of Khera s hypothesis include the fact that his literature review was retrospective, there was a potential selection bias arising from the general tendency not to publish negative data, and the failure to adequately address maternal toxicity endpoints in the published literature of the time. In fact, Khera himself stated that in 40% of the studies he evaluated in support of his hypothesis the maternal toxicity data were insufficient or nonexistent (9). 

Olanzapine had significantly positive diabetic effects, based on both duration of treatment and dosage. All patients had been exposed to antipsychotic drugs for more than 60 days because there was less awareness of the diabetic effects of atypical antipsychotic drugs during that period, the use of these data reduced the possibility of selection bias. 

The question of selection bias, that is the question that we are constantly working on. I would have to say that the drafts of what I have shown, with the exception of the freshmen data, were all longitudinal. 

As this example with p-dichlorobenzene shows the different levels of OELs are connected to differing scientific opinions on the harmful effects of the substance. The selection of what data to review obviously is important for the outcome of the risk assessment. It can also be concluded to not only being dependent on the time-related availability of the data. The potential for a selection bias of what literature to review in risk assessments has been shown by Ruden for the risk assessments concerning the carcinogenic properties of trichloroethylene (Ruden 2001). Although a case-study of acryl amide (Ruden 2004) shows that a selection bias by no means is an inevitable consequence. Another aspect of which the conclusions from a risk... 

Ambroise C, McLachlan GJ. Selection bias in gene extraction on the basis of microarray gene-expression data. Proc Natl Acad Sci USA 2002 99 6562-6. 

Conduct a pharmacoeconomic study Flexible Usually comparative Yields organization-specific data Reflects "usual care" or effectiveness Data from multiple sources can be used Expensive Time-consuming Difficult to control and randomize Potential for patient selection bias Potential for small sample size... 

Information bias—A flaw in measuring exposure or outcome data that results in systematic differences in the quality of information gathered for study and comparison groups. See also Selection bias. 

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