Weak validation refers to the use of inadequate, superficial, or poorly designed methods to verify the accuracy, reliability, or generalizability of a scientific result, model, or technique.

• Reliance on small or non-representative samples.
• Absence of a gold standard or lack of comparison to established methods.
• Use of subjective or qualitative criteria for evaluation.
• No replication, cross-validation, or external benchmarking.
• Failure to report sensitivity, specificity, precision, or other objective metrics.

• Undermines the credibility and reproducibility of results.
• Leads to overconfidence in exploratory or experimental tools.
• Can result in premature clinical adoption of unproven techniques.

“The authors claim accurate reconstruction of the oculomotor nerve using diffusion MRI, but the study suffers from weak validation: only 4 clinical cases are presented, with no intraoperative or histological correlation.”