[R] OT: P(Z <= -1.46).
rolf at math.unb.ca
rolf at math.unb.ca
Sat Nov 25 16:21:13 CET 2006
In checking over the solutions to some homework that I had assigned I
observed the fact that in R (version 2.4.0) pnorm(-1.46) gives
0.07214504. The tables in the text book that I am using for the
course give the probability as 0.0722.
Fascinated, I scanned through 5 or 6 other text books (amongst the
dozens of freebies from publishers that lurk on my shelf) and found
that some agree with R (giving P(Z <= -1.46) = 0.0721) and some agree
with the first text book, giving 0.0722.
It is clearly of little-to-no practical import, but I'm curious as to
how such a discrepancy would arise in this era. Has anyone any
idea? Is there any possibility that the algorithm(s) used to
calculate this probability is/are not accurate to 4 decimal places?
Could two algorithms ``reasonably'' disagree in the 4th decimal
place?
cheers,
Rolf Turner
rolf at math.unb.ca
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