How much bacteria growth occurs in reused water bottles?

Can someone help me identify variables?

• Question 1-How much bacteria growth occurs in reused water bottles? Question 2-Where are bacteria most present in a household? I need independent and dependent variables and constants

• Answer:

  Independent variables are what you have control over. Dependent variables are your results--the answer you obtain after modulating the independent variables. Question 1: You need to control the amount of initial bacteria. Either have the same person use all the water bottles or apply the bacteria by hand. Your independent variable could be the number of times the water bottle was used, and your dependent variable could be the number of different types of bacteria present when swabbed and cultured, or the size on the petri when cultured (larger colonies after a short time means there was a higher number of initial bacteria). Question 2: You don't have an independent variable except maybe location. The dependent variable would be the same as above.