Table 2 summarises the study location, inclusion criteria, randomisation method and study size and see Additional file 1 which summarises the characteristics of the interventions.
In addition, the program provides consultations in all matters related to sensory product testing: appropriateness of particular test method, study sample size, questionnaire design, statistics and analyses, sample blinding and serving sizes, to name a few.
Transformation to logits and weighting by the inverse variance as a method of adjusting for variable study size are standard methods for analysis of proportion data [ 15, 16].
It is possible that arsenic concentrations in the Danish drinking-water are below a low effect level; however, the results of the present study cannot rule out a weak adverse effect that is impossible to detect with the method used and the study size.
We extracted the following characteristics: methods (study design, sampling strategy, sample size, location, publication status), participants (recruitment, gender, age, proportion of SPFS), and outcome (accelerometer model used, number of days measured, cut-point used to define level of measurement, percentage respondents with valid measurements).
The data were extracted from each included study by two independent investigators, and the following information was collected: surname and initials of the first author, year of submission, country, ethnicity, language, age, gender, sample size, genotyping methods, study design, Hardy-Weinberg equilibrium test (HWE), SNP, and gene.
Our meta-analysis demonstrates that HPV detection method, continent, publication date, and study size contribute to the variability among individual study findings.
The multivariable model of HPV prevalence was adjusted for all study characteristics (i.e., HPV detection method, continent, publication date, and study size) (Table 2).
Among the RCTs reviewed, considerable variability was evident with respect to study size, randomization method, frequency of intervention repetition, potential bias, operational definition of adherence, identification of the intervention types, study follow-up, definition of standard of care, and inclusion criteria used.
To identify potential sources of heterogeneity between studies and to assess the effect of study characteristics on the results, we repeated the meta-analysis in strata defined by study size, design and method of data collection and ethnicity of participants.
