Should a client/customer be in the room or participating during planning poker?

Question

From my understanding, planning poker involves the development team or the executors of the project and the project manager or the project owner. I recently had a debate with our project manager on this issue about whether or not to include a client in this activity.Here are the arguments for both sides:**Cons:**I advocated against this because i feel if a client is in the room there is the possibility of changing our estimates and making them more optimistic than they are because the client is in the room.**Pros:**On the other hand, if the client is in the room they could provide and clear up requirements and let them understand the process and the value it could provide.**My Question**Therefore, my question is the following. In the best interests of estimation accuracy (i know it is almost impossible to be accurate), which it be best to include a client on this activity or preclude them?edit by said PM: Should be noted that in this case the client is both the project owner and sponsor.

Answer 1

The answer is yes if the following items are true;

1.     Your references to client, project owner, and sponsor are synonyms for Product Owner (PO).  The PO’s role is to clarify the developer's understanding of a user story by providing additional business insight, background, and specificity. 

2.     The client (PO) clearly understands that they cannot attempt to influence or control (i.e., bully) the developers in their questions, discussions, or estimates.   Examples of bullying would include making statements such as; I need it by a specific date, the last team I worked with gave me smaller estimates, I can’t live with that number, I don’t agree with your explanation, etc.  

3.     The client (PO) clearly understands that they “own” the specification (i.e., user story), while the developers “own” the estimate. Therefore, if the client disagrees with the developers, the only remedy is to modify the user story (e.g., decompose into smaller pieces, provide additional clarification, alter the specification, etc.), and the team will give a new estimate for the revised user story.

4.     The team trusts the client to represent the business in a knowledgeable fashion and without prejudice. The client trusts the team to provide their best unbiased professional estimates based on their experience and understanding.

5.     The client and team understand that the purpose of estimating poker is to develop relative sizing’s of user stories, not hour estimates. Also, the estimates should not be construed as the final number for the remainder of the project. Estimating the backlog is an ongoing process, not a one-time event. Extended efforts to achieve unnecessary precision violates the law of diminishing returns without providing additional value.  Planning poker is intended to keep the estimating process moving along, not get bogged down with extraneous (and often premature) details.

6.     The value of planning poker is the power of discussion, collaboration, mutual understanding, collective ownership, and rapid convergence on a reasonable estimate.