Roger Coppock wrote in message ...
[snip]
I would have added this feature earlier, but the 124-year record
shows warming so very strongly that special attention is required
to evaluate the "F distribution function" correctly. In most cases,
a simple table listing "F" values for 95% and 99% confidence will
do. (For an example, see this table from the "CO2 Science" site:
http://co2science.org/ushcn/ftable.htm) However, the positive
slope regression lines of global warming in temperature data series
have been more than 99% certain for over a half-century now.
(The positive correlation from 1880 to 1954 in the GISS land and
sea data set is about 99.9999999999% certain, with 73 degrees of
freedom and F = 75.92.)

I have therefore used the "BETAI" routine from "Numerical Recipes"
by William H. Press, Brian P. Flannery, Saul A. Teukolsky, and
William T. Vetterling in 1986. My results pass the test routines
provided by the authors, and they match the table from "CO2 Science"
as well. I've also checked my more extreme results, with their long
series of "9"s, against Wolfram Research's "Mathematica" version 3.0
for Macintosh. I used variations on these three commands:
Statistics'ContinuousDistributions'
$MaxExtraPrecision = 2000
N[CDF[FRatioDistribution[1, insertdegreesfreedomhere], Fratiogoeshere], 500]
This computation uses symbolic representations for numbers to simulate
many digits of precision, and is therefore a very slow process. A
single evaluation by "Mathematica," like the one needed to test the
case below, can take hours on my 266 MHz Mac G3 Power PC. In most
cases I tested, "Mathematica" and my implementation of "BETAI" agreed
on the number of "9"s; occasionally, they differed by a single 9 digit.


Here are the results for 124 years of GISS global land and sea data:
Rxy 0.833087 Rxy^2 0.694034
TEMP = 13.666145 + (0.004797 * (YEAR-1879))
Degrees of Freedom = 122 F = 276.73745
Confidence of nonzero correlation = approximately
0.99999999999999999999999999999999 (32 nines), which is darn close to 100%!
[snip]

I can save you hours of computing time. Use the calculator at
http://members.aol.com/iandjmsmith/FEX.HTM

Set it to calculate 1 - F distribution. With X = 75.92 and Denominator
df = 73 you get
Cumulative probability = 6.429602941527236e-13, so the F value is
1-6.429602941527236e-13

With X = 276.73745 and Denominator df = 122 you get
Cumulative probability = 3.644936641931845e-33, so the F value is
1-3.644936641931845e-33

I think you'll find lots of calculators can do the calculation this
accurately if they can work with the complement of (i.e. 1 minus) the
F distribution.

Alternatively, if you set the calculator to calculate F distribution,
then enter X = 1/276.73745, Numerator df = 122, Denominator df = 1 and
you'll get the same answer.

Now you can use a most F distribution calculators - even EXCEL gets it
right! It calculates the complement of the F distribution in the first
place so =FDIST(276.73745,1,122) gives 3.644936641694430E-33, a
relative error of approx 6.5e-11.

Ian Smith