G'day all.
Quoting "Mitchell, Neil"
With rounding to the nearest even integer for 0.5's you get 6, otherwise if you always round up you get 7. If you bias towards rounding up you get a general upwards trend as numbers are rounded, which is bad, while the even condition ensures that statistically it averages to the same thing.
There are also many numeric algorithms for which the rounding pattern in the least-significant digit is somewhat systematic. A simple example might be this: x <- round(x + 0.5) x <- round(x - 0.5) x <- round(x + 0.5) x <- round(x - 0.5) ... etc If you try this procedure starting with, say, x = 1.5, you can see a clear difference between round-up and round-to-even. With round-up, the rounding error is keeps increasing as the procedure continues. With round-to-even, the error is bounded. Cheers, Andrew Bromage