Doctors chase and Sanborn are conducting an experiment on effects of caffeine on memory. Participants are randomly assigned to a caffeine or non-caffeine group; there a recall on of items on a word list is later assist. Which pair correctly identifies a variable in this experiment?

The variable is the group that was given caffine, because thats what the doctors manipulated. They possibly altered the natural memory of the participants by giving them caffine. A more specific variable could be how much caffine each participant is given and what time are they given it.