Self-selected samples – When consultation respondents might be unrepresentative

An experienced consultation officer in the NHS recently could scarcely conceal her delight. The consultation had resulted in a 1% participation rate, regarded by her bosses and many others as being a creditable achievement.

In the cool light of another day, of course it may look differently. Not only does the arithmetic mean 1% is a very small proportion of the population, but it raises the question of what exactly made that 1% take part. After all, these people are normally self-selected. Indeed most consultation respondents have volunteered to give their views.