was highly significant (13.09 > 9.49). Significance of the inclusion of the drawing in the representation to findthe correct answer was high. The level of significance of the χ2 test has been chosenfor 2 standard deviations with σ = 0.05, 1-σ = 0.95; (n = 2 degrees of freedom for each column and n = 4 for theentire table). The Parson condition for χ2 test is fulfilled, less than 20% of cells smaller than 5 (Table 2).The poor performance of students having no drawing was significant beyond two standard deviation levels(sigma σ). Among the students who were shown the entire picture as well as students who were shown the pictureeither without vectors or without formula, 22% to 50% of found the right answer. In contrast, not one out of 23students could find the correct answer when the drawing was omitted. This result is highly significant (more than two sigma), while all other deviations from one group to another were less than one or two sigma.