Showing posts with label graphing. Show all posts
Showing posts with label graphing. Show all posts

## Saturday, August 2, 2008

### Issues with teaching graphing

Graphing is one of those topics where we underestimate the difficulty some students have interpreting and plotting data.

Try this at home. Plot a graph using height and weight as the axes. Show on the graph that Sue is heavier than Mary. John is the same weight as Sue. John is taller than Sue. Now, is Mary taller than John?

Of course it's a trick question but student answers are interesting and it is always worth investigating whether students are actually thinking when plotting data.

The next one comes with the age old problem of students not able to check answers. A student has ten values between 1 and 10. The calculator reports n=9, a mean of 11 and a standard deviation of 6. The student writes down the answer and moves to the next question.

To overcome these problems we need to model how to detect errors, make them on the board occassionally, reward those that spot the errors (and it's always a good time for a joke and prove that you are human after all) and emphasize how important error detection is. The teacher training adage that teachers are always correct and to hide or 'make intentional' any errors is to my mind poor modelling. My limited experience is that students connect with you as a person when you make 'honest' mistakes and own up to them, they are more willing to take risks and learn to use errors as a path to understanding.

At a content level, students find it difficult to grasp transformations of data within graphs (eg. scores->f->cf), pie charts (and the lack of understanding associated with ratios); relationships of median, quartiles and cummulative frequency in year 11; and mean weighted averages and seasonality in year 12. These areas require clear preparation and care especially when used in conjunction with graphics and CAS calculators.