Hour
Experimental Design
Roger works with the EPA (Environmental Protection Agency). His group
has noticed that the zebra mussels in the nearby river are beginning to die. Up
until now,, the mussel population has been healthy and lived in the river for
several years. Upon investigation, Roger discovers that a new factory was built up
river last year. Some of their waste is released into this river, but the company
insists that it is safe. Comparing river water samples from two years ago to ones
just collected, Roger detects two chemicals found in the new samples that are not
in the old ones.
Roger sets up two tanks of river water and zebra mussels collected at the
river. He separates the two new chemicals in separate tanks. He observes the
tanks for 48 hours. At that time, he notices that both populations of zebra
mussels are dying. He concludes that both chemicals are the cause of death to
the zebra mussels in the river.
1. What is the control in Roger's experiment?
2. What independent variable(s) is used?
3. How many experimental groups are used?
2 experimental groups
4. What was the control group for Roger's experiment?
5. What do you think Roger's hypothesis is?
6. Is Roger's conclusion a valid one? YES or NO
Why or why not?
7. What would you do differently to make this a good, sound experiment?