Abstract
Randomised clinical trials are designed to determine whether a particular treatment is appropriate to make a significant difference to the health of a defined population and to aid its approval for use. For an accurate, cheap and simple assessment to see if a treatment benefits an individual person, all that is needed is a pen, paper, simple pocket calculator and daily recording of a few variables. It requires the ability to read and write and to understand addition and division. Factorial design of experiments is used to show the impact of several variables and their interaction on the person's health status. An example of a 75-year-old man with an enlarged prostate is used here to illustrate this approach. This person was able to understand and reduce side effects, lower the costs of medication by 83% and improve measured health status by 28%. A multivariate model for this person was then created with about 450 person-days of data.