Table 2.
Mann-Whitney U test, paired-samples t test and Spearman-correlation analysis of water source types and well protection.
| TBC | TC | E. Coli | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| N | Sum of Ranks | Z | p | Sum of Ranks | Z | p | Sum of Ranks | Z | p | |
| Well seal | 1,614 | 1,388,953.5 | −8.69 | 0.00 | 1,423,757.0 | −4.95 | 0.00 | 1,435,982.5 | −2.52 | 0.01 |
| Well unseal | 175 | 212,201.5 | 177,398.0 | 161,595.5 | ||||||
| Wellhead above ground level | 1,172 | 793,316.0 | −3.15 | 0.00 | 792,041.5 | −5.47 | 0.00 | 804,776.5 | −2.33 | 0.02 |
| Wellhead below ground level | 209 | 160,955.0 | 162,229.5 | 148,113.5 | ||||||
| Well housing | 1,122 | 703,174.0 | −12.95 | 0.00 | 754,351.0 | −6.57 | 0.00 | 772,928.5 | −1.92 | 0.05 |
| No well housing | 264 | 258,017.0 | 206,840.0 | 186,876.5 | ||||||
| Surface water | 184 | 215,173.5 | −5.43 | 0.00 | 236,630.5 | −12.45 | 0.00 | 220,220.5 | −14.88 | 0.00 |
| Ground water | 1,737 | 1,630,907.5 | 1,609,450.5 | 1,616,265.5 | ||||||
| Well depth | 1,693 | - | 6.22 (t) | 0.00 | - | −30.07 (t) | 0.00 | - | −50.72 (t) | 0.00 |
| 1,693 | - | −0.15 (r) | 0.00 | - | −0.34 (r) | 0.00 | - | −0.11 (r) | 0.02 | |
TBC: total bacterial count; TC: total coliform; E. coli: Escherichia coli; N: the number of samples; Z: Z value of Mann-Whitney U test; p sig. (2-tailed); r: correlation coefficient of Spearman-correlation analysis; t value of paired-samples t test.