sandy harcourt

‘The Art of Statistics. How to Learn from Data’. By David Spiegelhalter. The very first Table in this book of 400 pages, Table 1.1 on page 23, ‘Outcomes of children’s surgery’ lists results of children's heart surgery from thirteen hospitals in the UK and Ireland. Three of the columns are numbers; two are percentages. The final line for all the columns is titled, ‘Total’. Total numbers is useful information. But what is a ‘Total’ percentage? In fact, the ‘total’ percentage is some sort of average. But what average? Mean, or median, or mode? Who knows which? The table legend did not tell us, and I certainly couldn’t be bothered to read the text to find out if it tells us. A book on how to learn from data begins with such a schoolboy mistake – presenting averages (of some unnamed sort) as totals - that I chucked it into my recycling bin. Alexander Harcourt Anthropology, UC Davis, CA.