Quantitative study: https://pubmed.ncbi.nlm.nih.gov/21986350/

Qualitative study: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5813303/pdf/14.pdf

review both the methods and the limitations stated by the authors to identify where there may be plausible threats to internal validity. The test of plausibility is more than just being possible. There needs to be some real expectation of likelihood. For quantitative research, the possible threats to study reliability include:

• subject fatigue,
• subject motivation,
• subject learning,
• subject ability,
• tester skill,
• different testers, and
• test environment.

For qualitative research, the possible threats to study validity include:

• rival explanations
• negative cases
• triangulation
• design checks
• participant reactions to analysis
• intellectual rigor