Determination of median in tabular and graphic context

Abstract: This study analyzes the responses given by 332 8th grade Portuguese students to two questions, one with data set defined by a frequency table and the other defined by a bar graph. The goal is the evaluation of the effect of the data representation on the calculation of the median. Using a combined methodology, a frequency analysis of students' response types and a semiotic analysis of responses, based on onto-semiotic approach of knowledge and mathematics education, were applied. The semiotic analysis' main goal was the identification of objects and mathematical processes, which can characterize semiotic conflicts implied from the student responses. Generally, students revealed greater tendency to not respond to the graphic determination of the median, however, those who do answer, tend to obtain the median with less difficulty in a graphic context. Semiotic conflicts seem not to depend on the presentation of the data set, although there are more answers that are incorrect in the tabular context than in the graphic context.