The three values of β0 chosen to define the slices were the midpoint and the limits of the 95% Bonferroni confidence interval for β0. corresponding to any particular point in the figure. Furthermore, the joint confidence ellipsoid for more than three parameters cannot be pictured. A more useful presentation of the joint confidence region is obtained by plotting two-dimensional “slices” through the ellipsoid for pairs of parameters of particular interest. This is done by evaluating the joint confidence equation at specific values of the other parameters. Three such two-dimensional ellipses for β2 and β3 are those shown in Figure 5.2. These slices help picture the three-dimensional ellipsoid but they are not to be interpreted individually as joint confidence regions for β2 and β3. Alternatively, one can determine the two-dimensional 95% joint confidence region for β2 and β3 ignoring β0. This region is also shown in Figure 5.2 as the larger ellipse on the floor of the figure. In this case, β2 and β3 are only slightly negatively correlated so that the two-dimensional joint confidence region is only slightly elliptical. The very elliptical slices from the original joint confidence region show that the choice of β2 and β3 for a given value of β0 are more restricted than the two-dimensional joint confidence region would lead one to believe. This illustrates the information obscured by confidence intervals or regions that do not take into account