Lead to errors relative to what? The mathematical idealisation or the actual practice?
Are you referring to this page?
https://en.wikipedia.org/wiki/Mortgage_calculator
"Since the quoted yearly percentage rate is not a compounded rate, the monthly percentage rate is simply the yearly percentage rate divided by 12."
Do you think that the explanation above is wrong?
In practice interest payments are calculated in many "wrong" ways, but that's what it is:
https://en.wikipedia.org/wiki/Day_count_convention
It's not necessarily wrong, but it's missing any disclaimer about which interest rates they're talking about so if you don't know what you're doing it will lead to mistakes.
(Of course any other definition of monthly rate will also lead to mistakes when it's inconsistent with the definition of yearly rate.)
https://en.m.wikipedia.org/wiki/All_models_are_wrong
Lead to errors relative to what? The mathematical idealisation or the actual practice?
Are you referring to this page?
https://en.wikipedia.org/wiki/Mortgage_calculator
"Since the quoted yearly percentage rate is not a compounded rate, the monthly percentage rate is simply the yearly percentage rate divided by 12."
Do you think that the explanation above is wrong?
In practice interest payments are calculated in many "wrong" ways, but that's what it is:
https://en.wikipedia.org/wiki/Day_count_convention