Every Scrum team member should be assigned 100% to that team with no other responsibilities.
This dramatically increases an individual’s productivity because you have no “lost time” when the person has to switch from one project to another.
When any person is working on a task, then has to switch to another task, there is a delay as the information for the first task is unloaded from the top of the brain and the next task is loaded in. The more complex the two tasks are, the longer the delay. A programmer keeps a lot of rules and information in his/her head while working on particular code. When he/she switches to a different project, there are new rules and information to remember. He or she has to “forget” the first set of rules and information, and “remember” the second set. This takes some time. The same is true for UI designers, writers, architects, and other other knowledge worker on the team.
A person can lose 20% of their possible working hours to switching between two projects. The lost time grows dramatically as more projects are added.
Now this has some implications for companies that are designed to optimize the individual. The company puts people in specialized roles, discourages them from doing anything outside that role, sets up their workstation to support that role, defines career progression for that role, etc.
Switching to a model that optimizes the team changes all that. We get rid of roles (except Scrum Master and Product Owner). Everyone is a Team Member. Individuals learn new skills and they have more software on their workstations to support those new skills. (f you don’t do that, then you have specialists sitting around doing nothing when their bit is completed. That makes no sense.)
Every member of the Scrum team should be prepared to help with any task that the team needs to complete, which encourages cross-training. People can pair up on tasks, where one person is experienced on that task and the other new to it. This is a very fast way for people to learn new things.
With a team of what Scott Ambler calls generalizing specialists, then everyone is working all the time, and you do not have time lost when people switch between projects.
Geri