Mean, Median, and Mode of the Blackwater Creek Data
Part 1

This study is a continuation of past studies in Lynchburg, VA, that measured a water pollution problem in Blackwater Creek due to sewage overflow. In the old sewage system, installed at the beginning of the 1900's, rain water from residential and street gutters plus sewage from homes and businesses flowed into the pipes. However, the city grew and the pipes in the sewage system could no longer handle the load. Sewage started to leak out of the pipes during rainstorms and run into water sources like Blackwater Creek. This produced high levels of fecal coliforms. Now, a new system is being implemented to eliminate the problem. In the new system rain water and sewage are carried away in separate pipes.

In this activity, you will be calculating the mean, median, and mode for the fecal coliform data of Blackwater Creek. The data consists of fecal coliform counts at three different sites along the creek. At each site data was collected on dry days and on days after it rained.

The data was collected in the fall of 1998 at three sites in order from Sandusky downstream to the Farm Basket, and Hollins Mill. Complete these activities to find out whether the new sewage system is reducing the sewage flow into the creek at all three sites. At the time the data was collected the new sewer system was completed upstream from Sandusky and the Farm Basket.

Using the data set in Excel, calculate the mean, median, and mode for each site on the dry days and on rainy days.

1. What are the mean, median and mode of fecal coliforms on dry days AND wet days at Sandusky?
2. What are the mean, median and mode of fecal coliforms on dry days AND wet days at Farm Basket?
3. What are the mean, median and mode of fecal coliforms on dry days AND wet days at Hollins Mill?

Sometimes, looking at data sets in a different way can reveal some interesting traits that were not detected by an initial analysis. Generate a line graph showing the dry and wet means at the three sites.

4. What does the graph tell you?
5. Is there a trend in the graph?

Now go on to Part 2 of this activity where you will compare 1998-99 data with data from past studies.





Original work on this page provided by Jon Giffin, Shirley Isaac, and Nykia Douglas (Class of '00).

Copyright © 2011 Central Virginia Governor's School for Science and Technology Lynchburg, VA