Determining the Optimal Team Size for your Project
If the data suggest that optimal team size is related to project scope, it should be able to help us find the right staffing strategy for projects of various sizes. In a study conducted in the spring of 2011, QSM Consultant Don Beckett decided to explore the best team size for different project sizes and management goals. He divided 1920 IT projects completed since 2000 from the QSM database into four size bins: less than 4000, 4001 – 9400, 9401-25000, and over 25000 SLOC. For each of these size bins, he determined median effort (SLOC/PM) and median schedule (SLOC/Month) productivity values. Based on the results, he assigned projects to one of four categories:
|Better than average for effort & schedule||Worse than average for effort & schedule|
|Better for effort/worse for schedule||Worse for effort/better for schedule|
As the chart below shows, projects in the smallest size quartile (under 4000 SLOC) using teams of 3 or fewer people (blue bars) were the most likely to achieve balanced schedule and cost/effort performance. Teams of 2 or fewer (purple) achieved the best cost/effort performance and teams of 2-4 (yellow) delivered the best schedule performance. Teams that used more than 4 peopleachieved dramatically worse cost/effort and schedule performance (green bar). This process was repeated for projects in the next 3 size quartiles and the results were entered into a team size matrix:
Don’s results confirm the findings from our previous two studies: the maximum optimal team size for cost/effort performance increases steadily with project size. The relationship between schedule performance and team size is less clear, with the optimal team size for balanced schedule and performance falling somewhere in the middle.