Dr. Jones was doing a formal research study of the effect of mental imagery on memory. She randomly assigned students in the psychology course she was teaching into two groups and required them to complete the task as part of their coursework. Forty students were in each group. Each group was presented the same list of thirty word pairs (e.g., tree/book, house/street, friend/cat). Group A was told to form a mental image for each pair. Group B was not given that instruction. Each group was given two minutes to memorize the pairs of words. Dr. Jones then tested their recall of the list by giving each group the first word and asking them to remember the second word. Dr. Jones recorded the number of words recalled by each group and then debriefed the participants. The results are presented in the table below.