Examining teachers’ knowledge of line graph task: A case of travel task

Teachers should possess a robust knowledge of graph interpretation in a world that requires increasingly scientific citizens. This study aimed to investigate teachers’ knowledge of interpreting a context-based line graph, by understanding the types of difficulties teachers have in interpreting such graphs. The study also sought to determine whether there were gender differences in teachers’ graph interpretation skills and determine whether these interpretation skills were different among teachers with varying teaching experiences. Sixty-one teachers from ten districts in one Indonesian province participated in this study. Empirically derived items were developed to identify the teacher’s conceptual understanding of line graphs with Curcio’s (Journal for Research in Mathematics Education, 18(5), 382–393, 1987) level of interpretation applied to explain the difficulties encountered. This study revealed that most of the teachers had difficulty answering questions that required ‘reading beyond the data’. Specifically, these teachers interpreted the graph as an iconic representation of a real event rather than an abstract representation of data (i.e., speed vs. time). Performance differences in teachers’ understanding of the graph were dependent on the grade level they taught, with differences especially evident in the interpretation of moderate and difficult items. There were no differences in teachers’ understanding by gender or years of teaching experience. The results highlight the importance of focusing on teacher professional development centering on teachers’ knowledge of graph comprehension.