Jeff worked for the CDC (Center for Disease Control). A report came in that
several workers in an office building were sick and had the same symptoms as
each other. They also worked in the same area of the building together. This had
been going on for two months. A small test was performed. All surfaces in the
affected area were swabbed. Each swab was put onto a petri dish with nutrient
agar to give any bacteria present some food. The dishes were allowed to sit for 3
days in a warm, dark cabinet. Upon inspection of the dishes, one came up with an
unusual bacterial growth. Jeff's problem now was that the growth was very
similar to two different kinds of toxic bacteria. He needed to determine which
toxic bacteria it was so they could treat the infection properly.
Jeff decided to use a sample of each suspected bacterium and grow them
on separate petri dishes using the same type of agar as before. He put both
dishes in a warm, dark cabinet. After three days, he compared dish A and dish B
to the dish from the office building. Dish A was definitely a match.
1. What was Jeff's independent variable?
2. Name the controls Jeff had in place during the experiment:
3. What was the control group?
4. What was the experimental group(s)?