To the extent that selection bias may exist, the effect is likely to be small.
Publication bias may exist when nonsignificant findings remain unpublished, thereby artificially inflating the apparent magnitude of an effect.
Finally, a measurement bias may exist since emotional distress and psychological status may not have been adequately assessed and controlled for all subjects [56].
Furthermore, an empirical bias may exist if analyzing the internal spending in one bank instead of total spending to examine the effect.
Second, as it was obviously not possible to perform a blind study, a potential bias may exist, particularly for experts and investigators.
However, many sources of bias may exist in a shotgun metagenomics protocol.
Besides an overall bias in the signal intensity, which is corrected for by the simple scaling normalization procedure, additional probe specific bias may exist.
Therefore, selection bias may exist.
Consequently, unexpressed bias may exist.
Consequently, unexpected bias may exist.
Finally, publication bias may exist.
