Internal validity describes the extent to which the (treatment) difference observed in a trial (or a meta-analysis) is likely to reflect the ‘true’ effect within the trial (or in the trial population) by considering methodological quality criteria. Because the ‘truth’ can never be assessed, it is more appropriate to speak of the potential for or risk of bias.
Please find the guideline on internal validity at the bottom of this page
This document is part of the JA1 Final Technical Report as Deliverable
NOTE: For the full Technical Report, please follow this link.