I'm having no luck finding any URLs, but if you look at histories of many physical constants, you see that new measurements tend to lie within error ranges of t

I'm having no luck finding any URLs, but if you look at histories of many physical constants, you see that new measurements tend to lie within error ranges of the most recent previous measurements. But occasionally, there's a jump to a substantially different value. The explanation is that scientists debug their setups and equipment until they get a result that's plausible, relative to prior published measurements. Because otherwise, people would be driven to figure out what they did wrong. And it could be embarrassing. But once they do, they tend to stop tweaking, and publish. So it's only scientists who don't manage to get plausible results, and yet are confident that they've debugged well enough, who publish results that end up becoming new standards.