What's the correct way to round, or estimate, a number to a specified precision?
Starting with wikipedia:
Rounding a number twice in succession to different precisions, with the latter precision being coarser, is not guaranteed to give the same result as rounding once to the final precision except in the case of directed rounding. For instance rounding 9.46 to one decimal gives 9.5, and then 10 when rounding to integer using rounding half to even, but would give 9 when rounded to integer directly.
That just makes no sense to me. What's the justification for different results? If
9.46 rounds to
9.5 why doesn't it then round to
I didn't ask the question correctly. The question, I think and hope I mean to ask, is why, or how, perhaps, double rounding and regular rounding can give different results (using half to even), and I suppose the answer is that there are different rounding algorithms which give different results.
I was thinking there should be one, correct answer as to what
9.46 rounded to the nearest integer rounds to. Double rounding, apparently, gives ten while "regular" rounding gives 9. Guess it just seems odd or weird to me to not double round.