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Table 2 Risk of bias of the studies, according to the Newcastle-Ottawa Scale adapted for cross-sectional studies

From: Pain level between clear aligners and fixed appliances: a systematic review

  Selection (maximum 5 stars) Comparability (maximum 2 stars) Outcome (maximum 5 stars) Total score (maximum 10)
Flores-Mir et al. 2018 [13] 4 1 3 8
  1. Newcastle-Ottawa Quality Assessment Scale (adapted for cross sectional studies)
  2. Selection (maximum 5 stars):
  3. 1. Representativeness of the sample:
  4. a)Truly representative of the average in the target population. * (all subjects or random sampling)
  5. b)Somewhat representative of the average in the target population. * (nonrandom sampling)
  6. c)Selected group of users.
  7. d)No description of the sampling strategy.
  8. 2. Sample size:
  9. a) Justified and satisfactory. *
  10. b) Not justified.
  11. 3. Non-respondents:
  12. a) Comparability between respondents and non-respondents characteristics is established, and the response rate is satisfactory. *
  13. b) The response rate is unsatisfactory, or the comparability between respondents and non-respondents is unsatisfactory.
  14. c) No description of the response rate or the characteristics of the responders and the non-responders.
  15. 4. Ascertainment of the exposure (risk factor):
  16. a) Validated measurement tool. **
  17. b) Non-validated measurement tool, but the tool is available or described.*
  18. c) No description of the measurement tool.
  19. Comparability (maximum 2 stars):
  20. 1. The subjects in different outcome groups are comparable, based on the study design or analysis. Confounding factors are controlled.
  21. a) The study controls for the most important factor (select one). *
  22. b) The study control for any additional factor. *
  23. Outcome (maximum 3 stars):
  24. 1. Assessment of the outcome:
  25. a) Independent blind assessment. **
  26. b) Record linkage. **
  27. c) Self-report. *
  28. d) No description.
  29. 2. Statistical test:
  30. a) The statistical test used to analyze the data is clearly described and appropriate, and the measurement of the association is presented, including confidence intervals and the probability level (p value). *
  31. b) The statistical test is not appropriate, not described or incomplete