no measurement is free of bias. why did you choose a particular instrument to take your measurements on? Why did you use a bruker NMR instead of a varian NMR? Was it because one manufacturer is german and the other is american? Why did you report your measurement in kcal/mol instead of kJ/mol? How does that affect the ability of a reader to glean insight from your report? Why did you even do experiment X at all? Was it because a reviewer told you to do it otherwise it wouldn't be published? Was that reviewer a former post-doc of a vicious competitor, who had a petty dislike for your previous advisor that had to do with the way that he answered a question she posed at a conference fifteen years ago?

So in subtle (and usually insignificant but always nonzero ways) politics can creep into these "measurements".