One potential source of error for modeling widespread species is that subspecies and/or races of species are frequently pooled for analyses, which may mask biologically relevant spatial variation within the distribution of a single widespread species.
Furthermore, the differences in treated patient groups or fractures and outcome measures between studies may have masked relevant differences between the techniques under investigation in published studies.
Moreover, grouping interventions according to a taxonomy may mask important and clinically relevant heterogeneity within different instantiations of what is nominally the same intervention.
On the other hand, focusing on very long-term mortality, which is extremely relevant to healthcare-cost issues, may mask beneficial effects of drugs used to treat sepsis if the patient dies later on as a result of an underlying chronic illness associated with a risk of sepsis [ 23].
Further, use of annual average PM2.5 concentrations may mask important shorter-term variations in true exposure profiles relevant to respiratory morbidity.
The traditional dichotomy of employed versus unemployed is still relevant, but it is rather crude and may mask potential differences in service use.
Such aggregation may mask area-specific changes in suicide rates over this period; analysis of relevant data revealed that although pesticide suicide rates did decline over this period, the reduction was similar in rural and urban areas (32%and33%3% respectively).
This effect would be particularly relevant in populations of conservational concern, where an apparently healthy census population may mask small Ne (Nunney and Elam 1994; Frankham 1995).
Also, patients may mask their feelings.
Statistics, however, may mask fundamental problems in malaria-endemic regions.
