Weekly sampling gives us important information, but the larger data set allows us to understand trends in water quality. Each week different locations come back with elevated and unsafe levels, but what does that mean about the overall water quality for that area? Long-term water quality is best understood by calculating the geometric mean, which is similar to an average, but is more accurate over a long time period. The geometric mean represents the typical value of data collected at one location, and is less influenced by outliers, like a very high value one week. Looking at these values instead of week-to-week results helps us identify and address long term water quality issues in our communities.