The article "Multimodal Versus Unimodal Instruction in a Complex Learning Environment" (J. of Experimental Educ., 2002: 215-239) described an experiment carried out to compare students' mastery of certain software learned in two different ways. The first learning method (multimodal instruction) involved the use of a visual manual. The second technique (unimodal instruction) employed a textual manual. Here are exam scores for the two groups at the end of the experiment (assignment to the groups was random):
Does the data suggest that the true average score depends on which learning method is used?