In the previous chapter we have seen how a simple statistical model can be fitted to data by estimating the unknown parameters and then making checks with residuals. After we have done this, various questions can be answered in terms of the fitted model. For instance, in Example 2.1, the question #xDoes fibrin level vary with time after injection?’ is put in terms of the F-test, β=0, in Section 2.4. The question ‘Between what limits do we expect the mean fibrin level to be at t=20?’ is answered by Exercise 2.4.3.