@heddaio Data quality typically is understood by six ‘dimensions’ - Validity, Completeness, Uniqueness, Consistency, Accuracy and Timeliness. The first four can be assessed programmatically, but the last two cannot.
Just because data exists, is valid and is plausible, does not mean it is correct! The data about me could state I have a full head of hair, analysing the data in isolation is unlikely to spot a problem, but checking against my profile image, you can see the data is inaccurate.