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 the experiment: Lupe is testing different brands of antibacterial soap to see which kills the most bacteria. The independent variable is what's manipulated.

• Option A: The tenth Petri dish is a control, not a variable.
• Option B: The brand of soap is manipulated (different brands are used), so this is the independent variable.
• Option C: The amount of soap (10 mL) is constant, not a variable being tested.
• Option D: The type of bacteria (E. coli) is constant, not manipulated.

Answer:

B. the brand of antibacterial soap