STAT 13
Introduction to Statistical Methods for the Life and Health Sciences
Laboratory 4 - Data Generation and STATA Coding
In previous labs, we have compared several data sets and looked for relation-ships
between paired data. In this lab, we will use all our previous commands
to reveal the story that the data tell. In place of the step by step directions,
you will need to select the commands as you need them.
About the Data
These data, from a study by Peter Nonacs at the UCLA Department of
OBEE, involve the foraging habits of thatch ants and seed harvester ants
and the strategies that these ants use to balance their ability to collect food
and their exposure to risk. The data were collected at the Sierra Nevada
Aquatic Research Laboratory (SNARL) in the Great Basin Desert Province.
. use "htttp: //www.stat.ucla.edu/labs/datasets/tant.dta"
Data description:
Each ant is classified by colony to distinguish ants from the same colony
from ants from other colonies. The distance from the mound’s entrance is
measured in meters. Each ant’s mass or wtmg measures the amount of food
or energy for that ant. Headwidt is the measure of an ant’s head at its widest
section and V5 is a scaled measure of headwidth. Worker class or size class
sorts the ants by their headwidths. Colony, distance, and sizeclass or worker
classes are categorical variables and mass or weight and headwidth are nu-merical
variables.
Lab Questions
- How large was the sample of thatch ants?
- How many colonies, distances,
and size classes were involved?
- Graph and then describe the distribution of masses for the thatch ants
in this study. Include the shape, center, and spread of the distribution. Are
1
there any outliers or unusual observations?
- How heavy is a typical thatch
ant?
- Graph and the describe the plot for the headwidths of the thatch ants.
Include the shape, center, and spread. Are there any outliers or unusual
observations?
- Graph and then describe the relationship between the mass and headwith
of the thatch ants.
- Graph and describe the relationship between distance from the mound
entrance and mass.
- Compare headwidths to determine if the thatch colonies produce different
sized ants?
- Do heavier or larger ants tend to travel farther from the mound in search
of food?
Assignments
- Now download the data for the seed harvester ants.
- Repeat the process for this species.
- How do the two kinds of ants compare with respect to their size and their
foraging habits.?
Last modified on
by 
.
Ivo D. Dinov, Ph.D., Departments of Statistics and Neurology,
UCLA School of Medicine