The aim of this paper is to present the concept of an 'instrumental' obstacle. In French agricultural education, the spreadsheet is often used as a tool or "artefact" in statistics teaching. Some obstacles to learning appear due to the use of this instrument. Difficulties appear during the learning of analysis of variance by students, who are not trained mathematicians. The concept of average however, which might have been regarded as unproblematic, caused surprising difficulties during one step in the algorithm for analysis of variance. The notion of 'instrumental' obstacle seems to be pertinent in order to analyse this phenomenon. This kind of obstacle is different from those presented by the internal constraints of the artefact. This study confirms that students have yet some problems with the notion of average, but that with spreadsheet use they become aware of this difficulty.
- Prof Dev