This study reports from a pre-service teacher's online learning and assessment activity on determining variability of two graphical artefacts. Using a critical-analytical perspective to data, the present study indicates that the prospective teachers surveyed showed awareness of relevant subject specific operators and methods; however, these seem not be well coordinated and were submerged in forms of expressions characterized by intuitive methods and everyday language. Significantly the prospective teachers seemed to substitute statistical and mathematical methods with explanatory metaphors which while providing room for deeper subject specific engagement were however, only used superficially. Their reliance on everyday forms of expression and visual perception is perceived as a factor that might have hampered their effective choice and application of relevant subject specific tools and forms of expression. This observation puts to task the role of informal methods in statistics education.