Should we include the stories done by part-time team members in team velocity

I'd like to share my thoughts on team velocity and the math behind it: https://mahdiziaee.com/index.php/2020/09/04/the-best-techniques-in-task-estimation-and-prioritization/

Ideally, velocity is not calculated for the greater good but for some tangible use. The answer simply depends on the use of velocity and the corresponding availability of these part-time team members. E.g. , in general, the 2 main uses of velocity are:

• giving estimations on 'milestones' and
• limiting the story points at Sprint planning.

In both cases, team capacity can be used for adjusting velocity to the situation, thus we do not expect the same velocity when fewer people are available.

It is also good to keep in mind that velocity is not only stochastic but has a terrible variance, so use it with caution.

Teams Have Velocity; Team Members Don't

Tracking velocity at the individual level is a common agile implementation error. It often occurs when teams or organizations are misusing velocity as a productivity metric or management target. Please don't do that.

The point of velocity is to provide an aid to capacity planning. To be effective in estimating team capacity, all work done by the team needs to be included in the metric. Unless you've structured your user stories to treat these part-time resources as externalities (something not in evidence in your original post), their work must be counted as work performed by the Scrum Team.

If you don't include part-time members in your velocity metric, you are skewing the results. In particular, not including their work in your team metric will:

1. reduce the team's ability to track the impact of part-time team members on overall team capacity;
2. create "hidden work"; and
3. cover up a key indicator of resource contention or organizational dysfunction.

CodeGnome's Law of Transparency says "No invisible work, ever!" That means that any work performed by any member of the Scrum Team must be accurately reflected in the trailing metric of team velocity, and properly accounted for when estimating current team capacity during Sprint Planning.

Include part-time team members' work also in team velocity

Looks like you have their part-time commitment in every sprint.

It often happens that some team members with specialized skills may be shared across teams. Let us say the two are 50% in your team, you can think of it as one additional person in the team and count their work in the velocity.

Even if they may not be able to attend the full Sprint Planning, consider asking them to call in when their work is discussed so that they can be more effective in their work.