Question

lupe is conducting an experiment to find out what type of antibacterial soap kills the most bacteria
in her experiment, lupe grows e. coli bacteria in ten different petri dishes. lupe then sprays 10 milliliters of an antibacterial soap on nine of the petri dishes. each of the nine petri dishes is sprayed with a different brand of soap. lupe doesnt spray any soap on the tenth petri dish
in lupes experiment, what is the test variable (independent variable)?
a. the tenth petri dish
b. the brand of antibacterial soap
c. the amount of soap sprayed
d. the type of bacteria grown

Explanation:

To determine the independent variable, we analyze what's being manipulated. Lupe uses different brands of soap (while keeping other factors like soap amount, bacteria type, and the tenth dish as a control consistent). The independent variable is the factor changed to observe its effect. Here, the brand of antibacterial soap is the manipulated factor. Option A is a control group, C is a constant (10 mL), D is constant (E. coli). So the independent variable is the brand of soap.

Answer:

B. the brand of antibacterial soap