Figure 4. Geometric Representation of the Confidence Interval Problem where the Minimum Width Interval is on a Boundary of the Parameter Space ⊝. Just as in Figure 2 the optimal interval is represented by the point at which the first contour line toes the feasible region. In this case the first line (with θ_H - θ_L= .2161) touches at a corner of the feasible region. This plot Illustrates the case where we desire a 95% confidence level for a Bernoulli parameter with n = 20 and to = 1.