Professor Karina Butler:

Anecdotally, if I were to treat someone like that, I would not necessarily know whether there was a temporal association with the antibiotic or a causal association. My knowledge that the antibiotic has had an effect is based on the studies that have shown people treated with it improve and those who are not treated with it do not. Where there is an intervention and something happens, the question always arises as to whether there is a temporal association or a causal association. To know that difference, we have to examine the science and trials that compare similar groups of people, one of which receives the intervention and one of which does not. This is to determine whether the benefit is evident only among those who receive the intervention.