My data is his data. As I've stated before, that's one thing we all have in common. The data is the same for everyone.
However, the data is not perceived by every the same way. A person with Paranoid Schizophrenia does not perceive the data of reality in the say way others do. Same data, different assessments of the data.
That is why (one of the reasons) we have the scientific method. So there is an objective means to evaluate that data.