Skip to Main Content
Table 4

Do you know of or suspect that any of the following pollutants affect either surface or groundwater quality in your area?

PollutantPrimary drinking water sourceNMeanS.D.F-valueBonferroni post hoca (Cohen's d)b
Pathogens (bacteria, viruses, germs) Private supply 32 1.94 0.72 3.069  
Public supply – municipal 254 2.06 0.66   
Public supply – rural water district 43 1.86 0.68  Bottled water (0.50) 
Bottled water 103 2.19 0.64   
Fertilizer/Nitrates Private supply 33 2.09 0.80 2.269 No significant differences 
Public supply – municipal 256 2.32 0.66  
Public supply – rural water district 43 2.14 0.74   
Bottled water 105 2.36 0.61   
Fertilizer/Phosphates Private supply 33 2.06 0.79 2.8532 No significant differences 
Public supply – municipal 254 2.33 0.66  
Public supply – rural water district 44 2.11 0.72   
Bottled water 103 2.35 0.61   
Heavy metals (lead, arsenic, mercury) Private supply 32 1.84 0.63 1.253 No significant differences 
Public supply – municipal 256 2.03 0.68   
Public supply – rural water district 45 1.96 0.67   
Bottled water 105 2.09 0.64   
Minerals (iron, manganese, calcium) Private supply 33 2.09 0.72 0.401 No significant differences 
Public supply – municipal 255 2.12 0.67   
Public supply – rural water district 44 2.14 0.70   
Bottled water 105 2.20 0.66   
Pesticides Private supply 33 2.09 0.77 4.100  
Public supply – municipal 252 2.33 0.67   
Public supply – rural water district 45 2.00 0.74  Public supply – municipal (0.48); Bottled water (0.50) 
Bottled water 105 2.33 0.61   
Salinity (water too salty) Private supply 33 1.42 0.50 3.873 Bottled water (0.70) 
Public supply – municipal 255 1.71 0.70   
Public supply – rural water district 45 1.69 0.73   
Bottled water 104 1.88 0.69   
Pharmaceuticals (antibiotics, personal care products) Private supply 33 1.73 0.67 4.223 Public supply – municipal (0.50); Bottled water (0.56) 
Public supply – municipal 254 2.08 0.69   
Public supply – rural water district 45 1.84 0.64   
Bottled water 105 2.10 0.65   
Petroleum products Private supply 33 1.76 0.71 4.530 Bottled water (0.64) 
Public supply – municipal 256 2.05 0.69   
Public supply – rural water district 45 1.87 0.66   
Bottled water 106 2.19 0.66   
Algae Private supply 33 1.82 0.77   
Public supply – municipal 255 2.13 0.70   
Public supply – rural water district 45 1.91 0.67   
Bottled water 105 2.11 0.64   
Product and waste water from mining Private supply 33 1.39 0.61 4.893 Bottled water (0.72) 
Public supply – municipal 252 1.69 0.61   
Public supply – rural water district 46 1.61 0.68   
Bottled water 105 1.85 0.65   
Septic systems Private supply 33 1.73 0.80 0.779 No significant differences 
Public supply – municipal 255 1.86 0.67   
Public supply – rural water district 45 1.93 0.75   
Bottled water 105 1.91 0.64   
PollutantPrimary drinking water sourceNMeanS.D.F-valueBonferroni post hoca (Cohen's d)b
Pathogens (bacteria, viruses, germs) Private supply 32 1.94 0.72 3.069  
Public supply – municipal 254 2.06 0.66   
Public supply – rural water district 43 1.86 0.68  Bottled water (0.50) 
Bottled water 103 2.19 0.64   
Fertilizer/Nitrates Private supply 33 2.09 0.80 2.269 No significant differences 
Public supply – municipal 256 2.32 0.66  
Public supply – rural water district 43 2.14 0.74   
Bottled water 105 2.36 0.61   
Fertilizer/Phosphates Private supply 33 2.06 0.79 2.8532 No significant differences 
Public supply – municipal 254 2.33 0.66  
Public supply – rural water district 44 2.11 0.72   
Bottled water 103 2.35 0.61   
Heavy metals (lead, arsenic, mercury) Private supply 32 1.84 0.63 1.253 No significant differences 
Public supply – municipal 256 2.03 0.68   
Public supply – rural water district 45 1.96 0.67   
Bottled water 105 2.09 0.64   
Minerals (iron, manganese, calcium) Private supply 33 2.09 0.72 0.401 No significant differences 
Public supply – municipal 255 2.12 0.67   
Public supply – rural water district 44 2.14 0.70   
Bottled water 105 2.20 0.66   
Pesticides Private supply 33 2.09 0.77 4.100  
Public supply – municipal 252 2.33 0.67   
Public supply – rural water district 45 2.00 0.74  Public supply – municipal (0.48); Bottled water (0.50) 
Bottled water 105 2.33 0.61   
Salinity (water too salty) Private supply 33 1.42 0.50 3.873 Bottled water (0.70) 
Public supply – municipal 255 1.71 0.70   
Public supply – rural water district 45 1.69 0.73   
Bottled water 104 1.88 0.69   
Pharmaceuticals (antibiotics, personal care products) Private supply 33 1.73 0.67 4.223 Public supply – municipal (0.50); Bottled water (0.56) 
Public supply – municipal 254 2.08 0.69   
Public supply – rural water district 45 1.84 0.64   
Bottled water 105 2.10 0.65   
Petroleum products Private supply 33 1.76 0.71 4.530 Bottled water (0.64) 
Public supply – municipal 256 2.05 0.69   
Public supply – rural water district 45 1.87 0.66   
Bottled water 106 2.19 0.66   
Algae Private supply 33 1.82 0.77   
Public supply – municipal 255 2.13 0.70   
Public supply – rural water district 45 1.91 0.67   
Bottled water 105 2.11 0.64   
Product and waste water from mining Private supply 33 1.39 0.61 4.893 Bottled water (0.72) 
Public supply – municipal 252 1.69 0.61   
Public supply – rural water district 46 1.61 0.68   
Bottled water 105 1.85 0.65   
Septic systems Private supply 33 1.73 0.80 0.779 No significant differences 
Public supply – municipal 255 1.86 0.67   
Public supply – rural water district 45 1.93 0.75   
Bottled water 105 1.91 0.64   

aAs in Hu & Morton (2011), the categories shown below are the ones that show significant differences (at 0.05 level) from the group being considered.

bCohen's d shows effect size for the difference between two means. In general, the value is calculated by dividing the difference between the two means with the standard deviation (or pooled standard deviation). Usually a Cohen's d of 0.20 means small effect, 0.50 is moderate effect, and 0.80 is large effect. Practically, a Cohen's d falling between 0.25 and 0.50 is considered significant (Cohen 1988; Hu & Morton 2011).

Close Modal

or Create an Account

Close Modal
Close Modal