Papers were also excluded if they reported a sample size less than 50, had unclear sampling methods or they contained no primary data, although the references were searched to gather primary studies not identified by the search.
These studies had some important limitations, however, including the lack of data on covariates at the individual level, unclear sampling methods, and use of highly skewed, untransformed PbB concentration data in analysis-of-variance models.
Thus our analysis investigated the relationship between ethnicity and suicide attempt in clearly defined psychiatric and ethnic groups, whereas many previous analyses have mixed or unclear samples which are unable to elucidate this relationship in these patient groups exclusively.
Papers were excluded if they reported a sample size less than 50 (except in countries where limited data were available) had unclear sampling methods, or they contained no primary data, although the references were searched to gather primary studies not identified by the search.
The mechanism by which Bcl2 protein is upregulated is unclear; sampling additional time points throughout pre- and postexposure to examine miR-34a and Bcl2 levels, and experiments examining the effects of miR-34a overexpression or suppression in the presence and absence of BaP would shed light on the complex interactions between miR-34a, its target genes, and DNA damage response.
In three trials, some posterior power calculations were performed (Portenoy et al, 1989; Walsh et al, 1992; Mignault et al, 1995) and in one study it is unclear whether sample-size calculation was performed (Stambaugh et al, 2001).
On the other hand, both biopsy and surgical samples are available for expression profiling for predicting clinical outcome by adjuvant therapy; however, it is still unclear whether surgical sample expression profiles are useful for prediction via biopsy samples, because little has been done about comparative gene expression profiling between the two kinds of samples.
Several of the quantitative papers were unclear about their sampling in terms of sample size justification [ 21, 25- 28]; power analyses were only reported in one of the quantitative papers [ 17].
In contrast, if conserved oligos (sequences surrounding the SNPs) are not used, then it is unclear whether the sample is a variant without that particular SNP, or whether the sample is degraded, the reaction conditions unsuitable, or the target species is not present.
