Final answer:
Medicare is a federal health insurance program that does not cover preschool children; instead, they are covered by the Children's Health Insurance Program (CHIP).
Step-by-step explanation:
Medicare is a federal health insurance program that provides coverage for various groups of people, including those over 65 years old, blind individuals, disabled widows, and patients with end-stage renal disease. According to the information provided, Medicare does not cover preschool children as they can be covered under the Children's Health Insurance Program (CHIP), which services children in families with relatively low incomes. Therefore, the group of people excluded from Medicare in the options provided is preschool children.