As our genealogy skills have developed, particularly over the last year, we are more often documenting our level of confidence in the facts and events we add to our family tree, or discuss in our posts here or in other documents we author.
There are many terms we could use to express our level of confidence, and many schemes to rank these terms relative to each other. No point in reinventing the wheel, though.
After purchasing a copy of Elizabeth Shown Mills’ Evidence Explained , we chose to adopt the hierarchy of terms presented there in Section 1.6 Levels of Confidence.
Certainly: The author has no reasonable doubt about the assertion, based upon sound research and good evidence.
Probably: The author feels the assertion is more likely than not, based upon sound research and good evidence.
Likely: The author feels some evidence supports the assertion, but the assertion is far from proved.
Possibly: The author feels the odds weight at least slightly in favor of the assertion.
Apparently: The author has formed an impression or presumption, typically based upon common experience, but has not tested the matter.
Perhaps: The author suggests that an idea is plausible, although it remains to be tested.
Being more mathematically and visually inclined, here is how we tend to apply these terms in our own use.
We usually keep possibly and apparently to ourselves until we have done a little more research.
When we estimate an individual’s birth year, based on a parent’s, spouse’s, or child’s birth year, we indicate this with, for example, “Estimate, based on her mother’s Birth.”
We assume the mother is 3 years younger than the father, and the mother is 22, 31, and 40 years old at the birth of their first, middle, and last child. These average ages were found in a reference that we unfortunately failed to record at the time. The reference though was for 1600–1900 America when the economy was largely agriculture-based.
And, if we copy something from someone else’s tree to preserve it until we have time to look at it, we now attach a source entitled “(copied from the internet; no source provided)”—copy these at your own risk!
 Elizabeth Shown Mills, Evidence Explained, Citing History Sources from Artifacts to Cyberspace, Third Edition, Revised (Baltimore, Maryland: Genealogical Publishing Company, 2017), 19-20.