http://www.ck12.org Chapter 1. An Introduction to Analyzing Statistical Data
Observational Studies
FIGURE 1.
Small Ground Finch, Santa Cruz, Galapa-
gos Islands.Some of the other famous residents of the Galapagos that have provided scientists with a wealth of information and
opportunities for study are the so-called Darwin’s finches. Each of the numerous species of finches has developed
special adaptations that allow it to survive in a particular area. There are ground finches, tree finches, cactus finches,
medium-billed, small-billed, and large-billed finches, just to name a few. One particular variety has even learned to
use a stick as a tool to dig for bugs. To the untrained observer, it is almost impossible to tell them all apart, and on a
visit to the islands you will see them everywhere!
Two researchers from Princeton University, Peter and Rosemary Grant, spent over 30 years studying the adaptations
of finches to environmental conditions on a small island in the Galapagos called Daphne Major.
The Grants’ spent up to 6 months a year on this “rock” documenting how species with certain beak size and shape
would thrive in years when vegetation that suited those species grew well, and would dramatically decrease in
numbers in years when that vegetation was sparse. This type of long-term approach to collecting data by making
detailed observations is called anobservational study, and is a widely used method of gathering data. In an
observational study, the researcher observes the population of interest and records the results without making an