Final answer:
Private goods offered to individuals organizing for a collective benefit are called selective benefits. Interest groups might provide these to encourage participation and overcome the free-rider problem associated with collective goods.
Step-by-step explanation:
Private goods made available to people who organize for a collective good are called selective benefits. Collective goods, such as public safety, environmental protection, and public education, benefit the general public and are nonexcludable and nonrivalrous. This means they cannot be withheld from individuals and can be used by many without depletion. Private goods, in contrast, offer particular benefits to individual consumers who can be excluded from using them if they do not pay for them.
Interest groups may provide selective benefits to incentivize membership, since individuals might otherwise refrain from joining due to the ability to benefit from collective goods without contributing to the effort or cost, a scenario known as the free-rider problem.