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Check the data semantics. Is the meaning of the data elements clear and unambiguous? For data elements with ambiguous meaning, try to improve their definition. For this, it might help to find out what is look into the intended value range of a variable - is the exact range known and is it clear enough?
In the example of collecting data on a patient’s 'sex', it might be unclear if it means ‘biological sex at birth' or ‘gender’. In another example, 'age' of a subject can be expressed in years, but in some cases (i.e. , such as studies with small children) , could also be expressed in months. It should therefore be clearly stated if the value range for age should be expressed in years or months.
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