Medical Statistics: Testing hypotheses
In the fourth article in our series on medical statistics, Wai-Ching Leung explains how to stack evidence against the null hypothesis
An important use of medical statistics is to draw valid conclusions from observations. For example, we might identify a group of patients with brain tumours and another group of people without brain tumours, ask them about their previous mobile phone use, and conclude whether users of mobile phones are more likely than non-users to have brain tumours.
But we can never be absolutely sure about our conclusions. As we have already discovered in this series, statistics are often used when events are not entirely predictable.1 We usually only collect information on a sample. For example, when we collect information on 500 patients with a particular disease treated with drug A and another 500 patients treated with drug B, we then attempt to draw conclusions on the effectiveness of the drug treatments on all patients with such a disease. By chance, however, our sample of patients given one drug may be