In these non-representative cases, we accomplished the study by staining sections from whole tumour blocks in five cases, but representative tissue was lacking for three cases.
Among 11 studies, the risk of selection bias from the use of non-representative cases was low in seven and unclear in four studies.
The case-control study by Sahl et al. (1995) was based on a very small number of clinic-based cases of BCC (less than 50), and thus it was limited in power, susceptible to selection bias due to non-representative cases and controls and to faulty recall of past weight and height measurements.
A surgical biopsy is, for example, justified in case of a non-representative CB and in cases showing high-risk lesions or premalignant findings at CB (Shin and Rosen, 2002; Sydnor et al, 2007; NABON, 2008).
This discussion paper, to be launched by the FAO Land and Water Division at COP24 in Katowice today, evaluated twenty-one NBS case studies using a non-representative sample, to learn from successful and failed experiences and to identify possible causalities among factors that characterize the implementation of NBS.
In this discussion paper, twenty-one case studies of water management processes are analysed, using a non-representative literature survey, and checked to what extent they meet the requirements of the NBS implementation based on the criteria presented.
Furthermore, the RDS is a non-representative sample limiting the generalizability of these results.
In addition, case-control studies may overestimate risk due to a retrospective assessment of aspirin use or the selection of a non-representative control population.
A non-representative sample can lead to under- or overestimation.
This raises the issue of non-participation potentially creating a non-representative sample.
Among other sources of bias in case control studies, low response rates in controls may lead to a non-representative sample of controls and to confounding/residual confounding due to missing or insufficient control for other risk factors [ 36].
