Question

You are conducting an experiment to determine if increased ultraviolet radiation from the decrease in

the ozone layer is killing off frog tadpoles. After examining all of the data available in the library, you
decide to go with a hypothesis that increased ultraviolet radiation from the sun is killing off the tadpoles.
You design an experiment with a control and an experimental group. Group 1 involves 100 tadpoles in a
five gallon container of water, which is covered by glass (knowing that the glass will filter out the
ultraviolet radiation). Group 2 will be set up exactly like group 1, except that instead of being covered
with glass, it is covered with an acrylic plexiglass, which will not filter out the U.V. radiation. You then
place the groups outside for a period of a month, and observe the results.

Results
Group 1 Group 2
Number of tadpoles 100 100
started with
Number finished 96 96
Using this information, answer the following questions.
a. What is the experimental variable and what is the dependant variable?
b. Does the information from this experiment support the hypothesis?
c. If no, then what might be causing the decrease in frog populations?
d. Which is the control group, and which is the experimental group?
e. What is the difference between the two groups? Should they be
different in any other way?

Answer 1

A.
The independent variable (experimental variable) is the exposure to UV lights of the tadpoles because it is being varied. The dependent variable is the survival of the tadpoles, because it is the one being affected by the independent variable.

B.
The information from the experiment does not support the hypothesis because an equal number of tadpoles remain, while the hypothesis predicted that less would remain in the tank exposed to UV light.

C.
Other factors such as temperature of the water may be affecting the frog populations.

D.
The control group was the tank covered with glass and the experimental group was the tank covered with acrylic plexiglass

E.
The difference was that one group was exposed to the UV light, while the other group was not. No, they should not be different in any other way, because that may lead to inconclusive experimental results.