11. estimation-1

Software Engineering
 Estimation
 The SPM begins with a set of activities
that are collectively called Project
planning
 Whenever estimates are are made we
look into future concern and so there is
some degree of uncertainty in
estimation

 Observation on Estimation
 PM (manager) must have the ability to
estimate
 PM with the ability to know what will go wrong
before it actually does
 Estimation of resources, cost and schedule
for a software requires experience of past
projects and access to historical data

 Project complexity has a strong effect
on uncertainty that is inherent in
planning.
 Complexity is affected by familiarity with
past efforts
 Real time projects are always complex
 Project size also effect the accuracy of
the estimates

 If the requirements have been solidified
estimation is easy but if the requirement
are keep on changing estimation is
affects

 Project Planning objectives
 The objectives of software project
planning is to provides the reasonable
estimates of cost, effort and schedule
 These estimates are made at the
beginning of the project and must be
updated with the passage of time.

 Software Scope
 Estimation of scope
 Functional, non functional requirements.
Constraints

 Obtaining information necessary for
scope
 Things are always hazy at the start of
the project
 There must be some meetings between
customer and analyst for obtaining the
scope of project

 1st meeting question
 2nd meeting question
 3rd meeting question and so on

 Resources
 The 2nd task of software planning is the
estimation of resources required to
accomplish the software development effort
 The development environment-----Hardware
and software tools, Reusable components
and people

 Human Resource:
The no. of people required for a software
project can be determined only after an
estimate of development effort.
 Reusable Software component
Off the shelf components
Full experience components
Partial experience components
New components

 Off-the-shelf components. Existing software
that can be acquired from a third party or that
has been developed internally for a past
project.
 Full-experience components. Existing
specifications, designs, code, or test data
developed for past projects that are similar to
the software to be built for the current project.

 Partial-experience components. Existing
specifications, designs, code, or test data
developed for past projects that are related to
the software to be built for the current project
but will require substantial modification.
 New components. Software components that
must be built by the software team specifically
for the needs of the current project.

 Problem based estimation
 EV is calculated as
EV= (Sopt+4Sm+Spess)/6
There is a very small probability that the
actual size result will fall outside the EV

 COCOMO Model
Constructive Cost model
Three model
Model 1
Model 2
Mode 3

 Make Buy decision:
The software managers are often faced
with the problem of make buy decision.
In some cases it is cost effective to
acquire rather than internal
development

11. estimation-1

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