Planning Poker® combines expert opinion, analogy, and disaggregation into an enjoyable approach to estimating that results in quick but reliable estimates.
Participants in Planning Poker® estimating include all of the developers on the team. Remember that developers refers to all programmers, testers, database engineers, analysts, user interaction designers, and so on. On an agile project, this will typically not exceed ten people. If it does, it is usually best to split into two teams. Each team can then estimate independently, which will keep the size down. The product owner participates in planning poker but does not estimate.