Handling and interpreting data
The skilful use of graphical (and other) analysis, as a process to identify patterns and trends between variables, needs to be explicitly taught and later reinforced.
Interpreting data involves recognizing and describing patterns between variables. It is important that students have experience of experiments that generate negative gradients and curved best fit lines, as well as the more common straight ‘best fit’ line with a positive gradient. Encourage students to express patterns clearly, e.g. “the extension increases as the force increases”, rather than assuming something is known, e.g. “it increases as the force increase”. Also encourage them to describe relationships quantitatively whenever possible, e.g. “for every 1 N increase in the force, the extension increases by 2 cm”.
Selecting an appropriate kind of presentation
Being able to select an appropriate kind of presentation is an important skill. Encourage students to explain and justify their choices. For example, they should not assume that a line graph with a best fit line is always an appropriate method of presenting data.
These experiments yield data sets that are not suited to line graphs and so require alternative methods of data presentation:
- Absorbing radiant energy with different surfaces
- Radiation from black and shiny surfaces
- Simple electromagnet
Drawing straight line graphs
Students commonly have difficulty when selecting appropriate scales with units, plotting data points, and drawing of a best fit line (if appropriate). Each of these steps can be obstacles to identifying the relationship between variables. Providing partly drawn graphs can help support weaker students and build their confidence.
These experiments yield data sets that should produce straight line graphs: