Home > Portfolio Management > The Magic Number 7 (Plus or Minus 2)

The Magic Number 7 (Plus or Minus 2)

November 30, 2009 Leave a comment Go to comments

For years I wondered why so many things appeared in collections of 7 items. There are Snow White’s 7 Dwarfs, the 7 Deadly Sins, the 7 Wonders of the Ancient World, and the 7 Seas.

Nearer to home, local phone numbers have 7 digits, standard vehicle license plates have combinations of 7 or less letters and numbers (this is also true for most countries in the world), and of course there are 7 days in every week and 7 NFL players must be in the line of scrimmage for a legal formation. I even grew up near a town in southern England called Sevenoaks.

Then I learned about the principle disclosed by George Miller in 1956 that a person’s short-term memory span is approximately 7 items. That number increases for common items such as letters and digits, and drops to nearer 5 for more complex items such as long or unfamiliar words. Any more than that, and a person’s ability to remember any of the items drops off dramatically. So if designers wanted people to easily remember a group of items – be they dwarfs’ names in a children’s story, or a number for self-dial telephones – they kept to that limit.

Project and Program Managers can also make use of this principle by organizing their teams into “right-sized” groups, each one having a clear focus and responsibility. The scrum agile software development method, for example, suggests a team size of 7 ± 2 for any given sprint. More generally a team structure can be created based on 5 or less distinct groups of participants, each group having a different role and requiring different communication content and frequency from the Project or Program Manager:

The Core Team: This should have no more than 7 ± 2 members. Any more and the tendency to seek consensus will slow down decision-making. This team typically contains the key solution architects and change agents that collectively make the key decisions and drive the project forward. Its members are typically full-time on the project and accountable for its success.

The Extended Team: Many projects and programs are of such complexity that the Core team alone cannot contain deep enough knowledge of all the subject matter required to achieve its goals. Consequently a cross-functional virtual team of Subject Matter Experts and advisers is required with representatives from all impacted departments. Members of this Extended Team are brought in as required for specific issues, key reviews and checkpoints. Unlike the Core team, the Extended team members will typically have other day-to-day duties outside of the Project or Program.

The Implementation Team(s): These are the developers, testers, production, installation and support teams that make the output of the project a reality. Each should have a point person responsible for liaising with the Core team. If the project is large, use appropriate hierarchical structures to keep the number of direct Core team connections below the magic 7 ± 2. Otherwise the span of control starts becoming unwieldy.

Sponsors & Stakeholders: This team is often neglected when creating a project resource plan, but is absolutely essential to the success of it before, during and after project execution. This team requires regular high-level status reports and an awareness of key issues that may require their intervention (eg project resources, mass communications, etc). A good project dashboard will contain no more than 7 ± 2 categories of items to report.

Users: Last but by no means least, the eventual users of the output from a project – whether it’s a new software solution, a revised operating process or procedure, an organizational change, or all three – require targeted “what does it mean for me” communications that explain the impact of the project in terms of their specific jobs and roles. The magic number is used here to make sure that sufficiently small groups of Users are addressed such that the messages are meaningful to their work, and that the messages are delivered frequently enough to reinforce the message, but not so frequently that they lose their impact.

One notable group of items that exceeds this short-term memory span rule is the Ten Commandments. Perhaps that’s why so many people seem to be forgetting them in modern times?

  1. No comments yet.
  1. No trackbacks yet.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: