Teaching chance for real

This should read “teaching probability for real” but that would not attract as much attention, and attention is needed more than ever. Although most recent and most appalling news has been focussed elsewhere, readers may have seen reports on the severe flooding in Australia, in Queensland and New South Wales (NSW) regions. To give you some idea, Brisbane received 80% of its average annual rainfall in 3 days, and the flood mitigation dam built after the 1974 floods held back “four Sydney harbours worth of water”. The town of Lismore in northern NSW is no stranger to floods, but this flood was 2-3 m above all previous records, peaking at a new record height of 14.4 m. Flooding had also been experienced in some of the same regions a year ago. For the second year in a row, therefore, much has been written and debated in the media about floods, with politicians claiming it was a 1-in500 year or 1-in-1000 year flood (see, for example, Bureau of Meteorology shoots down NSW Premier Dominic Perrottet’s ‘one-in-1000-year’ flood claim j Sunrise (7news.com.au)), and with both risk assessment experts and media commentators saying that giving risk as “1-in-100 years” is “disastrous and meaningless”, accompanied by repeated explanations of what it means and what it does not. Some years ago, a medical specialist colleague whose work requires almost daily explanations to individual women of risks, both of future health and associated with treatments, told me that she now always gives risks in terms of probabilities, usually as percentage chance, having realised some considerable time ago that explaining in terms of 1-in-100 or 1-in-1000 was misleading and unfair to patients. Before readers reach for various pieces of literature to quote expertise to contradict the above, I am not advocating removing such expressions from teaching, as they play a valuable part in an overall, better balanced and less limiting approach. There are a number of useful lessons and messages in unpacking the above, but two key messages and advocacies are that: