This study developed a graphicacy assessment instrument which can (a) assess and measure pupils' progress in graphical understanding for the National Curriculum, (b) identify significant errors and misconceptions in graphing held by Year 10 Mathematics pupils and so (c) help raise teachers' awareness of their pupils' mathematical thinking.<br>A carefully constructed set of graphical problems related to the research literature and located in the National Curriculum was administered to a pilot group of pupils. The problems were deliberately posed in such a way as to encourage relevant isconceptions to come to the surface. The test was 'scaled' using Rasch methodology and a graphicacy measure results, with the main misconceptions plotted with the items on the same scale. The pupils producing the most common errors in the test were selected to take part in some group interviews to get an insight into their way of thinking and to collect evidence for discussion with teachers. Data from teachers' interviews and questionnaires were also collected to ascertain the curriculum validity of the ssessment and to probe their knowledge of their pupils' understanding.
The CAUSE Research Group is supported in part by a member initiative grant from the American Statistical Association’s Section on Statistics and Data Science Education