[R] Precision - or lack there of

[John Sorkin]

R 2.3.1
Windows XP 

I am surprised at the lack of precision in R, as noted below. I would
expect the values to be closer to zero, particularly the later examples
where the sample size is quite large.

> mean(rnorm(500,0,1))
[1] -0.03209727
> mean(rnorm(5000,0,1))
[1] -0.005991322
> mean(rnorm(50000,0,1))
[1] -0.0006160524
> mean(rnorm(500000,0,1))
[1] -0.001254309
> mean(rnorm(5000000,0,1))
[1] 0.0004633778
> mean(rnorm(50000000,0,1))
[1] -0.0001325764

I would appreciate any thoughts. Is the lack of precision due to
running on a 32-bit system?

Thanks,
John


John Sorkin M.D., Ph.D.
Chief, Biostatistics and Informatics
Baltimore VA Medical Center GRECC,
University of Maryland School of Medicine Claude D. Pepper OAIC,
University of Maryland Clinical Nutrition Research Unit, and
Baltimore VA Center Stroke of Excellence

University of Maryland School of Medicine
Division of Gerontology
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524

(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing)
jsorkin at grecc.umaryland.edu

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