Figure 1: Box plots of coverage probability, expected confidence width, and symmetry of coverage for the following 95% confidence interval methods: 1. GEE, 2. Ratio, 3. NB, 4. GEE*, 5. Ratio*, and 6. NB* with the sample sizes (m1,m2)=(30, 50), and dispersion parameters (ϕ1,ϕ2)=(0.1848, 0.2494) [(a),(c),(e),(g),(i),(k)], (0.25, 0.25) [(b),(d),(f),(h),(j),(l)].