You can not personally know data from any experiment you have not seen is not fabricated. You can test certain things with your own equipment. But certain things could simply be faked

You do not have access to the super expensive microscopes, telescopes, space ships or satellites. - Fake "science" data

You do not own dinosaur bones ( museums use replicas )

You do not own ancient manuscripts - Fake history

You do not have access to DNA samples taken for court trials - improper convictions