Independent vs Dependent
When two samples are Independent of each other, the subjects selected for the first sample in no way influence the way the subjects are selected in the second sample.
Example: if a group of 50 people were randomly divided into two groups of 25 people each in order to test the effectiveness of a new drug, where one group gets the drug and the other group gets a placebo, the samples would be independent of each other.
Two samples are Dependent if the selection of subjects for the first group in some way influenced the selection of subjects for the other group.
Example: For example, suppose you wanted to determine if a person’s right foot was slightly larger than his or her left foot. In this case, the samples are dependent because once you selected a person’s right foot for sample 1, you must select his or her left foot for sample 2 because you are using the same person for both feet.