Table 3 Summary of quality assessment of included studies with cross-sectional design (n = 61)

Sampling:

   1. Was probability sampling used?

   2. Are the participants likely to be representative of the target population?

a) Very likely

b) Somewhat likely

c) Not likely

   3. Was sample size justified to obtain appropriate power?

   4. Was sample drawn from more than one site?

   5. If there are groups in the study, is there a statement they are matched in design or statistically adjusted?

   6. Response rate more than 60%

Measurement:

   1. Reliability indices

   2. Factor analysis

Statistical analysis:

   1. Were p-values reported?

   2. Were confidence intervals reported?

   3. Were missing data managed appropriately?