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Radon Cluster Survey in North Dakota - 1989
During 1989, the Department began to retest those homes that
were greater than 20 pCi/l in the recently completed 1988 home
study. The home owners were asked to give names of neighbors that
might want to be tested. The neighbors were contacted and testing
began. This type of testing is referred to as a cluster survey.
The Cluster Survey indicated that a log normal distribution can
result from the subset of another log normal distribution of
radon test results. See Figure 2.
TABLE 4 - CLUSTER SURVEY STATISTICS BY PARAMETER
Arithmetic Percent of Samples
Number of Percent of Arithmetic Standard Greater than
Floor Samples Samples Mean Deviation 4 pCi/l 20 pCi/l
Basement 362 90.0 19.5 7.6 81.8 27.9
First 34 8.5 13.0 14.3 5.0 1.7
Second 5 1.3 12.8 14.7 0.5 0.2
Third 1 0.2 7.6 0 0.2 0.0
All 402 100.0 18.8 22.2 87.6 29.9
The county statistics, as found in Table 5, reflect high
arithmetic means in Stutsman and Bowman Counties and low
arithmetic means in Ward and Wells Counties.
The database contained 402 samples whose arithmetic mean was
18.8 pCi/l with a standard deviation of 22.2. There were 352 (87.6%)
samples with a radon concentration greater than 4 pCi/l. For
concentrations greater than 20 pCi/l, the 120 samples represented
29.9% of the samples.
The high percentages of samples greater than 4 or 20 pCi/l in
the basements indicates that basements should perhaps be tested
whether or not people live in the basement.
Table 5, the city/county statistics for the Cluster Survey
reveals that many cities have high averages, yet it must be
remembered that the cluster homes were all located close to a
home that was found to have a high radon concentration in the
1988 Home Study.
FIGURE 2 - Log Normal Distribution Graph 
Number of samples: 402
TABLE5 - CLUSTER SURVEY STATISTICS BY COUNTY
PERCENTAGE PERCENTAGE
NUMBER ARITHMETIC # OF SAMPLES # OF SAMPLES
OF ARITHMETIC STANDARD GREATER THAN GREATER THAN
COUNTY SAMPLES MEAN DEVIATION 4 pCi/l 20 pCi/l
Adams 6 16.3 12.0 100.0 33.3
Barnes 7 12.1 10.3 85.7 14.3
Benson 3 15.4 16.1 66.7 33.3
Bottineau 14 25.4 39.1 71.4 35.7
Bowman 5 34.7 39.4 80.0 40.0
Burleigh 20 10.8 13.5 65.0 15.0
Cass 30 17.4 14.5 93.3 30.0
Dickey 2 8.0 4.9 50.0 0.0
Dunn 10 17.5 7.4 100.0 40.0
Emmons 4 6.5 1.9 75.0 0.0
Grand Forks 88 18.2 11.1 100.0 33.0
Grant 5 17.8 13.1 80.0 20.0
Hettinger 2 10.2 1.5 100.0 0.0
Kidder 4 19.0 14.6 75.0 50.0
McIntosh 2 7.8 1.9 100.0 0.0
Mercer 18 16.6 17.4 77.8 22.2
Morton 22 16.3 15.3 77.3 31.8
Mountrail 2 9.8 2.4 100.0 0.0
Nelson 5 11.3 6.6 80.0 20.0
Pembina 43 23.2 16.2 93.0 44.2
Pierce 3 15.5 11.5 100.0 33.3
Ransom 7 21.6 28.0 100.0 28.6
Renville 6 13.7 8.8 100.0 16.7
Richland 8 15.0 15.5 50.0 37.5
Stark 43 19.6 34.3 86.0 20.9
Stutsman 4 40.2 29.9 100.0 50.0
Towner 4 10.9 5.9 100.0 25.0
Traill 2 26.6 18.5 100.0 50.0
Walsh 27 29.2 40.6 88.9 37.0
Ward 2 4.2 2.9 50.0 0.0
Wells 4 5.2 3.7 25.0 0.0
TABLE 6 - CLUSTER SURVEY STATISTICS BY CITY/COUNTY
PERCENT PERCENT
SAMPLES SAMPLES
NUMBER ARITHMETIC GREATER GREATER
OF ARITHMETIC STANDARD THAN THAN
COUNTY CITY SAMPLES MEAN DEVIATION 4 pCi/l 20 pCi/l
Adams 6 16.30 12.03 100.0 33.3
Hettinger 1 28.50 0.00 100.0 100.0
Mott 1 5.00 0.00 100.0 0.0
Regent 4 16.08 12.17 100.0 25.0
Barnes 7 12.06 10.34 85.7 14.3
Valley City 7 12.06 10.34 85.7 14.3
Benson 3 15.40 16.12 66.7 33.3
Brinsmade 3 15.40 16.12 66.7 33.3
Bottineau 14 25.41 39.13 71.4 35.7
Gardena 8 40.65 46.18 75.0 62.5
Maxbass 6 5.10 2.80 66.7 0.0
Bowman 5 34.74 39.45 80.0 40.0
Bowman 1 5.50 0.00 100.0 0.0
Scranton 4 42.05 40.96 75.0 50.0
Burleigh 20 10.78 13.49 65.0 15.0
Bismarck 14 10.00 10.14 64.3 14.3
Wilton 6 12.60 19.04 66.7 16.7
Cass 30 17.37 14.45 93.3 30.0
Casselton 3 10.57 2.59 100.0 0.0
Fargo 24 18.10 15.82 91.7 33.3
Hickson 1 25.70 0.00 100.0 100.0
Mapleton 2 14.65 1.65 100.0 0.0
Dickey 2 8.00 4.90 50.0 0.0
Ellendale 2 8.00 4.90 50.0 0.0
Dunn 10 17.47 7.39 100.0 40.0
Dunn Center 5 19.16 5.02 100.0 40.0
Manning 5 15.78 8.85 100.0 40.0
Emmons 4 6.48 1.90 75.0 0.0
Linton 4 6.48 1.90 75.0 0.0
Grand 88 18.16 11.12 100.0 33.0
Forks
Grand Forks 64 19.25 12.05 100.0 35.9
Larimore 3 13.47 0.12 100.0 0.0
Manvel 5 11.98 5.29 100.0 20.0
Northwood 5 10.62 2.37 100.0 0.0
Thompson 11 19.33 8.39 100.0 45.5
Grant 5 17.82 13.11 80.0 20.0
Elgin 5 17.82 13.11 80.0 20.0
Hettinger 2 10.20 1.50 100.0 0.0
New England 2 10.20 1.50 100.0 0.0
Kidder 4 19.00 14.56 75.0 50.0
Steele 4 19.00 14.56 75.0 50.0
McIntosh 2 7.80 1.90 100.0 0.0
Ashley 2 7.80 1.90 100.0 0.0
Mercer 18 16.58 17.41 77.8 22.2
Beulah 4 18.03 15.61 75.0 25.0
Hazen 10 12.37 14.31 80.0 10.0
Zap 4 25.65 21.91 75.0 50.0
Morton 22 16.25 15.32 77.3 31.8
Mandan 14 11.61 8.68 81/4 21.4
New Salem 8 24.36 20.25 87.5 50.0
Mountrail 2 9.80 2.40 100.0 0.0
New Town 2 9.80 2.40 100.0 0.0
Nelson 5 11.32 6.60 80.0 20.0
Petersburg 5 11.32 6.60 80.0 20.0
Pembina 43 23.16 16.19 93.0 44.2
Bathgate 3 30.53 7.55 100.0 66.7
Cavalier 7 22.71 16.43 85.7 57.1
Concrete 5 26.34 22.93 100.0 20.0
Crystal 6 10.12 7.73 83.3 16.7
Drayton 4 20.55 22.63 100.0 50.0
Mountain 2 22.10 4.00 100.0 50.0
Neche 5 32.70 16.20 100.0 60.0
Pembina 4 29.45 14.60 100.0 75.0
St. Thomas 3 22.43 4.22 100.0 33.3
Walhalla 4 19.50 19.33 75.0 25.0
Pierce 3 15.50 11.53 100.0 33.3
Esmond 3 15.50 11.53 100.0 33.3
Ransom 7 21.61 27.99 100.0 28.6
Englevale 5 24.48 32.04 100.0 20.0
Fort Ransom 2 14.45 10.15 100.0 50.0
Renville 6 13.67 8.85 100.0 16.7
Mohall 1 5.30 0.00 100.0 0.0
Tolley 5 15.34 8.78 100.0 20.0
Richland 8 14.96 15.53 50.0 37.5
Christine 2 24.00 16.60 100.0 50.0
Wahpeton 6 11.95 13.90 33.3 33.3
Stark 43 19.57 34.30 86.0 20.9
Belfield 30 20.24 37.90 86.7 20.0
Dickinson 13 18.01 23.92 84.6 23.1
Stutsman 4 40.20 29.89 100.0 50.0
Jamestown 4 40.20 29.89 100.0 50.0
Towner 4 10.88 5.93 100.0 25.0
Calvin 2 14.05 6.85 100.0 50.0
Rock Lake 1 5.90 0.00 100.0 0.0
Sarles 1 9.50 0.00 100.0 0.0
Traill 2 26.60 18.50 100.0 50.0
Buxton 2 26.60 18.50 100.0 50.0
Walsh 27 29.20 40.56 88.9 37.0
Edinburg 12 40.13 55.91 91.7 50.0
Grafton 12 20.97 18.92 83.3 25.0
Park River 3 18.43 3.00 100.0 33.3
Ward 2 4.20 2.90 50.0 0.0
Minot 2 4.20 2.90 50.0 0.0
Wells 4 5.23 3.69 25.0 0.0
Fessenden 4 5.23 3.69 25.0 0.0
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