Mean, Median, Mode and Standard Deviation of the BCNA Data

In this activity, you will be calculating the mean, median, mode and standard deviation of dissolved oxygen data for Buffalo Creek near Evington, VA, taken in August, 1997, during a descriptive field study conducted by CVGS students. Dissolved oxygen is an important parameter in determining the health of a stream ecosystem since it reflects the amount of oxygen available to aquatic life in the stream. Levels below 4.0 mg/l are dangerous for aquatic life.

Using the data set in Excel, calculate the standard deviation, range, mean, median, and mode for the entire data set.

1. Is there much difference between the mean and the median?
2. What about between the mean and mode?
3. Does Buffalo Creek have dissolved oxygen levels that indicate a healthy environment for aquatic life?
4. What does the standard deviation reveal about the dissolved oxygen data? Stated another way, are the data points closely clustered around the mean, or are they relatively spread out?
5. If most of the data falls between -1 and +1 standard deviation from the mean, what range would that encompass? List the lower and upper bound of that interval as well as the range of the interval.

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