EXAMPLE 10.19

Computing the predicted values and residuals. The first observation is a diameter of x = 2. The corresponding predicted value of gestational age is

= 15.1859 + (0.9185)(2)

= 17.023

and the residual is

= 16 − (17.023)

= −1.023

The residuals for the other diameters are calculated in the same way. They are −2.697, 2.548, 4.955, −6.474 and 2.689, respectively. Notice that the sum of these six residuals is zero (except for some roundoff error). When doing these calculations by hand, it is always helpful to check that the sum of the residuals is zero.