The methods of hypothesis testing I learned as a scientist are applicable to many situations, including testing the effectiveness of advertising. The “null hypothesis” – the assertion that nothing has changed – is central to the method. This has the effect of putting me (the testing expert) in a position that feels adversarial, to those who are trying to show an effect of their work. In NASPL Insights June 2014 I recount how my first encounter with a client exposed both my methods, and their feelings.