Children's Graphical Conceptions

In this paper we report the development and validation of a 'graphical assessment' tool and attainment hierarchy, based on a previous pilot and a main study (n=425) of 14 to 15 year old children. The items were developed from the research literature to suit the UK National Curriculum, and scaled using Rasch methodology. The result is a single dimension measuring graphicacy', which updates and extends Kerslake's CSMS hierarchy. Each level is described as a characteristic performance but now includes errors which diagnose significant misconceptions. The items and diagnoses (drawn a priori from the literature) were validated in group discussions and in general were consistent with previous work. We provide an analysis of one exception, i.e. Janvier's and Clement's 'slope-height' confusion, which we attribute to a new form of Leinhardt's 'Interval-point' confusion. Finally we argue that creating valid diagnostic tools is a prerequisite for the transformation of previous research findings into pedagogical content knowledge and hence of practice.