This exercise was inspired by research conducted by high school students in John Signorelli's Environmental Studies class at Whitney Point High School in Whitney Point, New York. Mr. Signorelli has been teaching his students how to monitor the water quality in Whitney Point reservoir for 5 years. In addition to learning about water quality and its importance, the students post their data on a web site as part of the Susquehanna River Watch Project. This project includes 10 schools in the Susquehanna basin that monitor water quality each fall and spring. In Mr. Signorelli's class, they use chemical test kits from HACH Company. This exercise was developed because of a discovery made with the nitrate test kit. Nitrate is a form of nitrogen considered to be an important aquatic nutrient.

While working with this class, we discovered that different people sometimes obtain different nitrate values with the same sample. We saw this as a "teachable moment" and realized that if the data were to be useful, the students would have to investigate the errors involved in using these test kits. We quickly realized that the things learned about measurement with the HACH kits were applicable to many forms of measurement.

The description (MS Word or PDF formats) explains the activity, and the accompanying MS Excel file shows example results.