In response to the State Children's Health Insurance Program in 1997, 37 states (including the District of Columbia) expanded Medicaid coverage to children in families below 200% of the poverty line, with even higher thresholds in some states.

a. In some of these states, the eligibility expansions have covered all children. How would you design a quasi-experimental analysis to evaluate the impact of these expansions?

b. In other states, the eligibility expansions covered only certain age groups of children. How could you design a quasi-experimental analysis to evaluate the impact of these expansions?

How could you make this more convincing than the evaluation in (a)? Explain.