ABSTRACT
Every day we are bombarded with messages from people who would like to sell us something – everything from products we don't need but might enjoy to political ideas that might persuade us to support their party or their cause. They often set out to make their case more persuasive by quoting numbers or displaying graphs that support it. But these are, inevitably, carefully selected from a very much larger set of data. How does a mathematically literate person best think through the options implied, to ‘buy’ or not to buy – as ever, without wasting time? That is the theme of this chapter. Much of what follows will be familiar to the reader, but we hope a broad overview will be thought-provoking.
