Furthermore, scientists reject all anecdotal evidence because they know that people are lousy observers and that sometimes they lie through their teeth. Accepting this kind of evidence does not guarantee that one will be wrong, but it always increases the possibility. So, to be scientific means accepting as your working hypothesis the least outrageous explanation you have for the data. You probably haven't heard this prescription before. I know that all of my teachers described science as some dispassionate pursuit of truth, devoid of prejudice or preconceptions.
People do research and people are prejudiced.
Indeed, these prejudices are absolutely necessary for science to advance because they keep scientists from wasting their resources chasing after silly notions. The trick is to develop the right prejudices. But either one is as careful as one can be to establish the reality of something, or one isn't. Probably because there are only material things. That is the least outrageous interpretation we can glean from careful inquiry, although I would happily change my mind should new evidence arise.