Frequently Asked Questions - Sizing
What options are available for sizing projects in SLIM-Estimate?
The Size Calculator offers a variety of sizing techniques that may be used individually or in combination. A common and flexible technique is Sizing by Decomposition, which allows you to break the system down into individual components such as epics, stories, features, RICEF objects, or your custom components, each of which can have its own gearing factor (IU/component). The individual component estimates are rolled up into a total size estimate, which will be posted back to the Solution Assumptions screen.
Instructions for using the Sizing Calculator and descriptions of each sizing method are available in SLIM-Estimate NetHelp.
QSM's Software Size Matters Infographic also provides a great general resource for which sizing unit to use at each point in the software lifecycle.
Please contact QSM Support for help creating your size estimates.
How can I change the unit for Total system size in the Balanced Risk and other solution wizards? Currently it is set to IU, but we use Function Points.
Solution wizards that require a size estimate assumption use the Sizing By History technique to obtain an initial "ballpark" estimate based on the statistical size ranges, or t-shirt sizes, in your project's associated trend group(s). This technique uses the Function Unit and Gearing Factor in the Project Environment settings. Most of the templates installed with SLIM-Suite have the Function Unit set to the Base Size Unit, either IU or SLOC.
To change the Function Unit to Stories, Features, Function Points, or other size unit, select Tools | Customize Project Environment from the menu. On the Project Description Tab, there is a Function Unit list box. Select Function Points or other unit, then enter an appropriate Gearing Factor to represent the average number of Base Size Units (elementary programming steps) contained in your selected Function Unit (ex.: a gearing factor of 50 represents 50 Base Size Units per Function Point).
If you need help determining an appropriate gearing factor, visit the Function Point Gearing Factors page on the QSM web site, download our Gearing Factors whitepaper, or contact QSM for assistance.
Three MS Excel sizing spreadsheets are installed with SLIM-Suite that can be used standalone or linked to SLIM-Estimate workbooks via the Sizing Calculator. This is the most flexible method, allowing unlimited sizing units, gearing factors, and uncertainty ranges for both. Spreadsheets can be distributed to subject matter experts who are not SLIM users, so they can contribute to sizing efforts.
Three sizing methodologies are available:
- PERT Decomposition
- Prioritized Features
- Relative Percentage
These spreadsheets are stored in the C:\user\Documents\QSM\Toolsxxx\Templates folder, where 'xxx' is your SLIM-Suite version number, e.g., 103.
You may download the spreadsheets and other templates on the Downloads page.
SLIM-Estimate's macro estimation approach uses product size and productivity to estimate project time and effort tradeoffs. Selecting the best sizing technique and units of measure can be challenging. The following resources help you understand basic concepts and how to use the in SLIM-Estimate .
- SLIM-Estimate Sizing Techniques Quick Reference
- Constructing Sizing Methods
- A Method for Improving Developers’ Size Estimates
- Gearing Factors: A Flexible Sizing Technique
The Code Counters page contains links to code counters for Java, VB, HTML, C++, Oracle PL/SQL, and many other programming languages.
The QSM Function Point Table provides SLOC/FP language gearing factors for a variety of programming languages.