This bias can be particularly severe when sample sizes of individuals are small, large numbers of markers are used, and true differences between groups are small (Anderson 2010; Waples 2010), all of which may apply to the current study.
Third, whilst our sample included participants with mild, moderate and severe HV, the sample size in the current study was not sufficient to examine subgroups according to HV severity.
However, that study had severe limitations: small sample size (146 participants), questionable selection procedure (i.e. shifted gender and age distribution; 91% were women with a mean age of 68 years), prevalence was reported without gender- and age-standardization, and a high prevalence of co-morbidity occurred (90% reported heart disease).
We cannot rule out a weak association of ethnic origin with mortality in patients who already have severe malaria, and our sample size may have been too small to detect a statistically significant effect.
Although the PPARγ2 12allelelele was associated with a lower prevalence of severe histological activity, the sample size is too small to cross the statistical significance threshold.
Even though the odds of lung disease were higher among the childhood pneumonia case-patients compared with controls (odds ratio 2.93, 95% CI 0.69 12.48), the study had severe limitations, including small sample size and potential bias (only 68 of 190 possible cases were traced).
As a result, the mothers were grouped according to the severity of their child's condition: mild and moderate/severe (moderate and severe conditions were collapsed together due to the small sample size of severe cases; see Results for details of this process).
In order to compare the proportions of newborns in propranolol group (treated) and control group (standard treatment), that progresses to more-severe ROP, the estimated sample size was calculated, considering normal distribution, an alpha error of 0.05 and a power of 80percentt.
Secondly, the relatively small sample size of severe stable angina patients might aggregate the ceiling effect.
Second, the rare but severe clinical scenario limits the sample size despite the long study period.
