220 
a probable deviation of 13.7 per cent from a 
mean of probable error of 1.8 per cent is 
significantly improved by using an estimate 
having a probable deviation of 9-7 per cent 
from a mean of probable error of not less 
than 5 per cent. Statistical treatment would 
probably show a slight advantage with the 
latter procedure in the long run, for the 
simple reason that it is based on more com¬ 
plete use of the data. But for practical pur¬ 
poses any statistical, long-run gain is can¬ 
celled by the evident risk of an aberrant 
estimate for a given year, as shown in Table 
4. If numbers of simultaneous checks for 
estimates were available, such aberrant esti¬ 
mates might be faced, but predictions of an¬ 
nual rainfall are checked one at a time, with 
an unavoidable concentration of interest on 
the one result. 
With the present span of data, the 
averages of rainfall cycles are so subject to 
disturbance by aberrant years that any given 
year’s prediction can be in error by 20 per 
cent or more. 
PACIFIC SCIENCE, Vol. 1, October, 1947 
It appears that there is at least a psycho¬ 
logical difference between estimate and pre¬ 
diction. For every practical purpose we are 
forced to the conclusion that the cycle analy¬ 
sis does not yield predictions of useful ac¬ 
curacy or reliability. To offer for a given 
future year, on the present basis, a definite 
prediction for public guidance in practical 
matters would be an unwarranted presump¬ 
tion. 
REFERENCES 
Alter, Dinsmore. A simple form of periodo- 
gram. Ann. Math. Statis. 8: 121-126, 1937. 
Board of Water Supply, Honolulu, Hawaii, 
Bien. Rpt. 11. 180 p. Honolulu, 1947. 
Johnson, Maxwell O. Correlation of cycles 
in weather, solar activity, geomagnetic values 
and planetary configurations, viii + 149 p. 
Phillips and Van Orden, San Francisco, 1946. 
Nakamura, Winters T. A study of the varia¬ 
tion in annual rainfall of Oahu island, based 
on the law of probabilities. U. S. Monthly 
Weather Rev. 41: 354-360, 1933. 
Wentworth, Chester K. Geographic varia¬ 
tion in annual rainfall on Oahu. 14 p., 4 fig. 
Hawaii Univ. Res. Pub. 22. Honolulu, 1946. 
