THE EXPERIMENTAL APPROACH: You have the hypothesis that the density of one of the frog species is a function of the distance from water. A hypothesis like this should have some underlying biological rationale, for example, that sites near water have a higher density of prey species (insects) and therefore frogs should occur at higher densities at theses sites. Based upon your hypothesis, you design an experiment to answer this questions, for example, sampling frog densities along a transect as you move away from the water. You would then use the appropriate graphical and statistical procedures to analyze you data to determine if you reject or fail to reject your hypothesis.
THE DESCRIPTIVE APPROACH: Several of the birds on the island exhibit interesting behavior, and in many cases this behavior has been poorly described. You chose to carefully document the behavior of one or more species of birds, and how this behavior varies over the course of the day, in relation to climate, or by sex. Note that the study might involve a very high level of quantification, however, no specific hypothesis is being generated or tested. Thus the study is descriptive. A similar example involves the measurement of aspects of the vegetation from site to site, either along a moisture gradient or an elevational gradient. If no specific hypothesis is being tested, this would also be a descriptive study.
Even though these studies are descriptive, in the sense that they are non-experimental, they involve the collection of data, and can often be very quantitative.
THE SURVEY APPROACH: This approach involves primarily the development of lists or sequences of qualitative information. We have had several very valuable group projects done in the past of this nature (the guide to the ferns of Springfield, the photographic guide to the herps of Dominica). These projects tend to be non-experimental and not quantitative (thought species lists with relative abundance estimates is an exception). One generally must have a certain level of taxonomic expertise to do species lists.
The video approach has been little explored. Options include video documentation of tourist damage to parks or a video documentary of a particular species.
Be objective.Avoid introducing your own bias into the sampling procedure. Select sites and transects either randomly or regularly. Observe your study organism so that you document the full range of behavior.
Replicate.Select multiple sites for each of your experimental groups. Avoid the trap known as pseudoreplication.
Sample intensively.The more data or observations that you collect, the better you will be able to test you hypothesis or describe the phenomenon that you wish to study.
Quantify.Collect quantitative data when the study dictates, and be careful with your measurement technique.
Understand the biology of your organism. Read about the organism you intend to study BEFORE you go to Dominica. Take along copies of articles or information from books that you can consult while on Dominica. You will do a much better project if your research is guided by some biological principles or understanding.