An investigator wants to study the relationship between endotoxin levels in children and their proximity to operating farms. Below are endotoxin levels in units per milligram of dust sampled from children's mattresses, organized by children's proximity to farms. Use an appropriate nonparametric test to test if there is a difference in endotoxin levels between children living within 5 miles of an operating farm as compared to those living between 5-24.9 miles. Based on this result, does proximity appear to affect endotoxin levels?