【转帖】rules for rounding decimals

yang686526

rules for rounding decimals
i have searched for rules of rounding and no luck.  ansi z210.1 and ansi/ieee 268.  anyone have an idea where i might find a standard pertaining to rounding, that will satisfy asme y14.5 or y14.41?
astm e 29 - 06 standard practice for using significant digits in test data to determine conformance with specifications
regards,
cory
let's make sure i understand the question, do you mean something in the asme standards that explcitly states that 1.50000000000000000... rounds up while 1.4999999999999... rounds down?
kenat, probably the least qualified checker you'll ever meet...
i was thinking in terms of rounding fractional equivalents, like .0625, .01625,.078125 to either 2 or 3 places.
and no, i do not propose using fractional equivalents on a new design unless driven by tool sizes or such.
the real problem occurs when the digit following the last place to be rounded to is 5.  for example .625 rounded to 2 places. do we make it .62 or .63?  at one time there was a rule which apparently is no longer existant.

in school, i learned an unwritten rule that says you should round a "5" to the even number unless there is some specific reason to round to the odd.  i was never given a reason for this rule.  i also do not believe it is explicitly stated in any standard.
there are standards regarding this kind of rounding in the statistics principle, but i do not know what the stadards are.  though, i do not believe they are applicable to engineering drawings since (from what i understand of them) they make some assumptions that may contradict asme y14.5m's rule regarding the absolute nature of dimensional tolerancing.
matt lorono
cad engineer/ecn analyst
silicon valley, ca
ringster, i think the same or very similar came up fairly recently, may have been a ringman post.  take a look.
kenat, probably the least qualified checker you'll ever meet...