Читать книгу Medical Statistics - David Machin - Страница 75

Categorical data are simply data which can be put into categories. Binary data are the simplest type of categorical data. Each individual has a label which takes one of two types. A simple summary would be to count the different types of label. However, a raw count is rarely useful. For example, there were 45 656 new cases of breast cancer registered in England in 2016. On its own this sounds like a large number, but there were 303 135 new cases of all cancers registered in 2016. Thus breast cancer accounts for 15.2% (45 656/303 135) of all new cancer registrations in England. Proportions are a special example of a ratio. When time is also involved (as in counts per year) then it is known as a rate. The mid‐year population of England in 2016 was estimated as 55 268 067. Thus, the breast cancer registration rate was 0.008 (45 656/55 268 067).