| Site | E. coli | Frequency | Total (%) | χ2 | P value |
| Not contaminated (%) | Contaminated (%) | ||||
| Commercial | 24 (15.0) | 56 (35.0) | 80 (50.0) | 11.5629 | 0.001 |
| Non-commercial | 7 (4.4) | 73 (45.6) | 80 (50.0) | ||
| Total | 31 (19.4) | 129 (80.6) | 160 (100.0) |