Final answer:
When Ned pays for a new refrigerator using an installment plan, it means he will make a series of payments over a period, rather than paying the full amount upfront.
Step-by-step explanation:
If Ned pays for a new refrigerator using an installment plan, the best description of the method of payment is that he makes a series of payments over time. This means he does not pay the full amount upfront in cash or by check, but rather, he commits to paying a certain amount on a regular basis until the total cost of the refrigerator is paid off. Installment plans are common for larger purchases as they allow individuals to spread the cost of the item over time, making it more manageable financially.