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 students of the Central Virginia Governor's School for Science and Technology. 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 either Excel or the TI-83 graphing calculator, calculate the mean, median and mode for the entire data set. Then, using either Excel or the TI-83 graphing calculator, calculate the standard deviation and the range for the entire data set.

This data exists in three files; one is in Excel Data format, one is in Text format, and one is in TI-83 Group file format. If you want to calculate the mean, median, mode and standard deviation using the TI-83, you will have to import the text data into the calculator from the computer after you have downloaded the file.

Is there much difference between the mean, median and mode? What does comparing the three statistics indicate? Does Buffalo Creek have dissolved oxygen levels that indicate a healthy environment for aquatic life?

What does the standard deviation reveal about the dissolved oxygen data? Is there a lot of variation in the data? Are the data points clustered around the mean or are they spread out? If most of the data falls between -1 and +1 standard deviation from the mean, what range would that encompass?

Copyright © 1997 Central Virginia Governor's School for Science and Technology Lynchburg, VA