The ratio of NDS mortality to cancer incidence may be more valid for the prediction equation since we used the equation to predict national incidence from national mortality, but we also expected the ratios to be less precise since they were based on smaller populations.
Thus smoothed SIR estimates are to some extent averaged over neighbouring values; this also helps address the problem of unstable empirical estimates that are based on small population sizes [ 15].
The full texts of both of these articles underwent critical appraisal [39, 40], and the studies resulted of good quality, even if based on small populations (40 enrolled in Muren et al.'s study and 53 in Nau et al.'s study).
Many of these reports, however, have been based on small populations and have used different forms of statistical analysis.
These studies generated inconsistent findings, were based on small populations, and focussed on short-term post-cholecystectomy outcomes (<5 days post-operatively) only.
While many previous studies have been based on small populations or aggregated data we have, for our purpose, access to a rich anonymized micro dataset, the so-called Linnaeus Database (25), containing, for instance, information from various administrative registers provided by Statistics Sweden as well as by the Swedish National Board of Health and Welfare.
These three studies, however, were all based on small study population and did not control for potential confounders.
Especially in studies based on small training population sizes, effects of relatedness may become of overwhelming importance [ 12, 13].
Results from non AIDS-defining cancers available from the few studies that were conducted so far are based on small-sized populations.
