Agnostics tend to be followers of the scientific method, which allows them to change their minds over what they believe as new - and sometimes better - information is unearthed to show why an existing belief is probably untenable,
Peer review is the process where noted specialists in a scientific field look at the work of researchers and pass judgement over the validity of the findings. And most of the time, this process weeds out honest mistakes some researchers make.
But the system is not infallible. And more to the point: not compulsory.