Software Estimation: Reviewing Size Estimates A presentation by QAI http://www.qaiglobal.com

1. Software
Estimation:
Reviewing Size
Estimates
A presentation by QAI
INDIA | USA | UK © QAI India Limited. All rights|reserved.
| CHINA | MALAYSIA
SINGAPORE

2. Reviewing Size Estimates
A SECoE Customer experience
Company Overview
A Global systems integration and business transformation consulting firm focused on the
communications industry. Chosen transformation partners for wireless and wire-line, and
broadband operators in Europe, Asia-Pacific and North America. Enjoy more than 60% of
business from British Telecom plc (BT), world leaders in communication service providers
Key Application Metric
Cost per FP Defects per FP
--------------------------------------------------------------------------------------------------------
Fig 1
Page 1 of 3

3. British Telecom over the last couple of years has been moving towards an IT environment which
is transparent and standardized in terms of its cost estimations and associated quality attributes
Standardization of all vendor estimates using the IFPUG based counting practices (4.2.1) was the
first step. The final goal is to help establish the total cost to deliver projects using the size based
FP measures, thereby creating a standardized metric to benchmark across all vendors and
consolidate productivity measures
Scope
QAI India Ltd. was approached for providing a third party review on the FP sizing methodology
being adopted (as a vendor) specific to development and COTS product customizations. While
this was the first step the overall scope was to calibrate the estimation model and help reduce
cost per FP
What is Function Point Method?
A function point is a unit of measurement to express the amount of business functionality an
information system provides to user
Consulting Methodology
Assess-Review -Report mode of consulting was followed. Initially the skills of the project
managers in the organization were assessed specific to the sizing techniques. A set of
Development projects and COTS products were reviewed for compliance to the Counting
Practices.
Compliance to FP counting practices was ascertained using the following broad headers:
(a) Valuation -The objective deals with whether items included in the function point count
should have been included. Perhaps the original count included additional transactions or
files that should not have been included
(b) Completeness - The objective deals with verifying or inclusion of all transactions and
files in the final function point
(c) Classification The objective deals with determining whether all transactions have been
classified appropriately as Low, Medium and High
(d) Mechanical accuracy Incase automated tools are not used, to check if accuracy of
calculations exist
An independent count report was also provided as a deliverable.
Next Steps
The process of progressively refining estimation accuracy consists of seven steps in sequence.
(Fig 1).
Step 1: Review Sizing Requisites
The existing practices being used for sizing projects and enhancements were reviewed for
compliance. This task will help codify and institutionalize the sizing expertise. Currently a 9%
variance (+ or -) in the sizing counts is observed
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4. Step 2: Standardize Sizing Sheets
Standardize sizing sheets, which contain a handful of attributes against which projects may be
measured. Non-FP effort can be converted and acts as an input to the Estimation Model
Step 3- Step 6: Review and Recalibrate
Review the estimate model for effort estimations by each stage of the life cycle. Review time logs
for accuracy. Without accurate effort data, it becomes impossible to reliably tune the estimation
model
Step 7: Analyze Variances
The differences between the predicted effort and the actual effort hold the key to improving the
accuracy of the estimated model. The estimated model is calibrated based on these variances.
Once the variances are stable and below an accepted threshold (say 5%) the attributes of the
sizing sheet and the project efforts are reliably correlated. The sizing sheet can thus be used as a
reliable predator for project effort and associated cost
Page 3 of 3

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