Repeated Trials 

The experiment was conducted three times, the reason for the repeated trials was to insure that the data was reliable. Although we cannot completely eliminate human error and the possibility of false positives with faulty trials, the presence of repeated trials reduces the likelihood of either of those. 

Test Subjects 

I used three different earthworms (one for each trial). It is important to use multiple test subjects to make sure your hypothesis is true for the whole group you are testing and not just your individual subject.