Confidence Interval for Seed Harvester Ant Data


In this activity, you will be calculating the confidence interval for the seed harvester ant data set.  The data for the file was collected at the Sierra Nevada Aquatic Research Laboratory (SNARL) in the Great Basin Desert Province. This study investigated the relationship between the size of the ants and the weight in milligrams of each ant. The units for the class sizes are arbitrary, corresponding to ruled increments that can be seen in the microscope with which the sample is measured.

Using the data set in Excel, determine the mean and the standard deviation for the weights for each class size in the seed harvester ant data set. Then, using these two values for each class size, calculate the confidence intervals for each class size in the seed harvester ant data set. .

1. What is the confidence interval for each size class using 90% confidence? 95% confidence? 99.7% confidence?
2. How do the confidence intervals change if you compare the 90%, 95%, and 99.7% confidence intervals for the <37 class ant?
3. Do you detect the same change in the other three classes?
4. Why does the range of the confidence interval changes as it does when you go from 90% to 95% to 99.7%?
5. What class would a fairly large group of ants having a mean weight of 59.4 mg likely belong to?


Original work on this document was done by Central Virginia Governor's School students Jonathan Kim, Steven Nash, and Corey Templeton (Class of '05).

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