Credible Estimationfor Small Projects

Rita Hadden

WDC SPIN February 2001

Where do we Start?

Estimation pre-requisites Estimation steps Defining size and complexity for your work Developing effort estimate for 1 work product Questions?

Estimation Pre-requisites

An accurate Work Breakdown Structure (WBS) drives reliable size estimates.

Include project management and quality management activities in WBS.

Focus on estimating key deliverables. If possible, compare with actuals from similar

past projects. Assume your first estimate will be wrong. Re-estimate at the end of key stages. Build re-estimation into your WBS.

Estimation Pre-requisites - 2

Record your estimating assumptions (rationale behind the estimate).

Assign WBS activities to individuals or labor categories.

Assume each task is performed by one person. Adjust for multiple people, or separate the tasks.

Estimation Pre-requisites - 3 Check your “bottom-up” estimates against “top-

down” estimates. What to ask when two or more estimates are

different:– Were requirements different?– Are the assumptions for the two estimates

similar?– Are there significant differences in people

assigned?– Is the product maturity factor a source of

variation?

What To Estimate?

Design Construction Documentation QA/Test Project Management Quality Management

When To Estimate?

After Completed Requirements After Completed High-level Design After Completed WBS

Estimation Definition Steps (one time)

1. Define size (small, medium, large).

2. Define complexity (simple, moderate, complex).

3. Create 9 categories of size/complexity combinations.

4. Use in-house subject matter experts to develop a “credible” effort estimate for each category.

Estimation Steps for Projects(recurring)

1. Assign each task a size and complexity rating.

2. Use the appropriate standard effort chart to determine the number of hours needed to perform task.

3. Assign “experience factor” and/or “product maturity factor” as appropriate.

Define Size and Complexity for Your Work

1. Think about what are the unique characteristics of the work you do that affect size and complexity.

2. Make these characteristics part of your size and complexity definitions.

3. Find the respected experts in your group for design, code, test, and documentation.

4. Get their effort estimates for each category based on its size and complexity definition.

Develop effort estimate for 1 work product

10-Minute Exercise:

Pick 1 work product you will be responsible for developing in the next 4 weeks. Estimate the size, complexity, and effort of the work product in 8 minutes or less. Record your rationale (estimating assumptions).

Develop effort estimate for 1 work product

Questions to consider:– What assumptions did you make in order to

complete the estimate?– On a scale of 1 to 5, with 5 the highest value,

how reliable is your estimate?– What information would you need to estimate

more reliably?