Interim Baseline Radiological Investigation Report in
Support of the Upton Rare Earth Processing Plant
November 15, 2012
8
3.2.1 Project-Wide Gamma Count Rates
Table 3-1 provides a statistical summary of the gamma count rates recorded in the Project.
Table 3.1. Statistical Summary of Gamma Count Rate Data
Estimator/Endpoint
Gamma Data (cpm)
Mean (arithmetic)
15,910
Standard Deviation
1,854
Median
16,091
1
st
quartile
14,687
3
rd
quartile
17,092
IQR
2,405
Minimum
8,637
Maximum
27,148
Counts
38,023
Notes:
cpm = counts per minute
IQR = interquartile range
Illustration 3.1 is a histogram of the frequency distribution of the gamma count rate data
collected within the Upton Project. A theoretical lognormal distribution is plotted as the smooth
line on the illustration, for the purpose of reference. The distribution peaks at approximately
16,000 cpm and tails off at approximately 11,000 (low end) and 20,000 cpm (high end). In
addition, the distribution appears to be bimodal and fails to approximate normal and/or
lognormal statistical tests.
Illustration 3.2 is a probability distribution plot, with the theoretical distribution (blue line) set as
normal. Approximately 99 percent of the points align with the theoretical normal distribution;
however, it cannot be described as normal because 1) there is a discrepancy between the
theoretical and actual distributions on the tails and 2) the data set does not pass the Anderson-
Darling Normality Test at a 95 percent level of significance.
Illustration 3.3 is a probability distribution plot, with the theoretical distribution set as lognormal.
The majority of points (approximately 99.5 percent) align with the theoretical lognormal
distribution; however, the distribution of gamma count rates cannot be described as lognormal
because there is a statistical discrepancy between the theoretical and actual distributions on the
tails.
