Population and sampling
Is the sampling method probability or nonprobability? Is the specific sampling method used in the study to obtain the sample identified and appropriate?
Is the sample size identified? Is a power analysis reported? Was the sample size appropriate, as indicated by the power analysis? If groups were included in the study, is the sample size for each group equal and appropriate?
Is the sampling process adequate to achieve a representative sample? Is the sample representative of the accessible and target populations?