This procedure is similar to that of the stratification in the statistical sampling, although the extraction of the cases has not been operated with randomized criteria nor determining the size of the sample on the basis of the sampling error.
Lastly, we wish to point out that since a randomized population-based sample from the city of Salamanca is involved, the information obtained may be of increased representativeness - particularly considering that many studies suffer bias due to the lack of purely randomized criteria in selecting the participants.
To further understand how SNP-pair compatibility probabilities depend on primer selection criteria, we randomized these criteria and evaluated the resulting graph density for 50 SNPs randomly chosen from human chromosome 21.
In spite of these limitations this feasibility study should provide knowledge to estimate important parameters that are needed to design the main study, (willingness of patients to be randomized, inclusion criteria, number of people eligible, follow-up rates, response rates and adherence/compliance rates) [ 22].
If the patients were not randomized, the criterion was assessed as 'not done' and it was assessed as 'not clear' if there were insufficient details of the allocation method.
We extracted information from both the abstract and the ClinicalTrials.gov record, including type of randomized comparison (parallel, cross over, cluster), multi-center status (yes/no), number randomized, and inclusion criteria related to demographic characteristics of the study population (i.e., adults, children, included sexes, presence of a disease or condition, and/or healthy volunteers).
Eligibility criteria Randomized controlled trials comparing screening flexible sigmoidoscopy with no screening.
However, a previous study reported that patients fulfilling similar clinical criteria randomized either to surgery or supervised exercises had better prognosis than patients given placebo laser [ 13].
We selected studies based on the following inclusion criteria: randomized, controlled trials comparing IV fluids of different Cl concentration in patients requiring volume resuscitation.
Eligibility criteria Randomized controlled trials, quasi-experimental studies, and cohort studies that assessed nasal decolonization or glycopeptide prophylaxis, or both, for preventing Gram positive surgical site infections compared with standard care.
Studies eligible for the present review met the following criteria: randomized, controlled trial study design; enrollment of adult patients with sepsis; presence of a hemodynamic goal for patient management; > 24-hour follow-up; and survival included as an outcome.
