STOCHASTIC SIMULATION OF RADIONUCLIDE UPTAKE
20
a
1S p-
7
|
|
3
NUMBER OF CASES
815
Lf
05
25
%s-, PC/G
it]
50
Fig. 8—Frequency distribution of bone Sr in 55 jackrabbits from
Jackass Flats, Nev.
are normally distributed. The total x’ with seven degrees of freedom,
is 2.57 (X? 9; = 14.07).
It may also be noted that Snyder and Cook**)*4 have analyzed the
frequency distributions of a number of stable trace elements in human
tissues (e.g., cadmium, copper, zinc, aluminum, and iron) and con-
cluded that all distributions are skewed to the right, with the sample
means exceeding the sample medians.
It is clear then that radioelements and trace elementsin thetissues of the individuals constituting a population do not always exhibit
normal distributions. In fact, normal distributions may prove to be
unusual, It is suggested here that a more likely expectation is a nonGaussian distribution skewed to the high side and often normal following a log transformation. Another possibility is given by Ellett and
Brownell,’ who analyzed measurements of 37Cg in 878 samples of
human muscle collected between 1959 and 1963. By normalizing the
data to eliminate the time variation, they were able to construct a
probability
histogram based on 670 samples.
This histogram was
clearly asymmetrical and skewed to the high side. Although a X’ test
indicated a probability of less than 1% that the distribution was log-
normal, Ellett and Brownell found that their observations could be
well fitted to a gamma distribution.