Read the following descriptions of experiments and answer the questions about them. You do not
need to actually perform any of these experiments, just answer questions about their design.
Experiment
You want to determine which disinfecting spray kills off more germs, Clorox or Lysol. You
spray two counters with juice from raw chicken. Then you spray one counter with Clorox and
one with Lysol. After the solutions dry, you wipe a cotton ball on the Clorox counter and then
wipe it onto a petri dish. You do the same with the Lysol counter and wipe it onto a separate
petri dish. You let the plates grow bacteria for several days, then count which plate has more
colonies of bacteria.
Questions
Name the Independent and Dependent Variables from the experiment above.
Name two good Control Variables you would keep track of in this experiment.
This experiment needs a Positive Control Experiment. (This means at least one more counter
and petri dish.) Describe what you would do to confirm that you can measure your experiment is
working as expected.
Create a hypothesis for this experiment. Remember that a good hypothesis doesn’t have to be
right, it just has to follow the rules. (Which spray will kill off bacteria best?)
