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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

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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