project estimation 2

8/3/2019 Project Estimation 2

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Out lineWhat is estimation

Objective of estimation

Why it is important? Project estimation process

Conclusion

Cocomo Model with example

Wideband Delphi Process

Compiler project example

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What is estimation? The definition of the verb estimate is to produce a

statement of the approximate value of some quantity.

Estimates are based upon incomplete, imperfectknowledge and assumptions about the future.

For these reasons, many estimates of software costs arenot 100% correct.

So, all estimates have uncertainty.

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Objective of estimation Effort / Cost

Schedule

Staffing Risk

Reliability

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why it is important? The project manager must set expectations about the time

required to complete the software among the stakeholders,the team, and the organizations management.

If those expectations are not realistic from the beginning ofthe project, the stakeholders will not trust the team or theproject manager.

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Project Estimation Process Ideally an estimate should be produced using the ten-step

process.1) Establish estimate scope

2) Establish ground rules & assumptions3) Collect data4) Size software5) Prepare baseline estimates6) Quantify risks & risk analysis7) Review, verify, validate estimate8) Generate a project plan9) Document estimate & lessons learned10) Track project throughout development

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1-Establish Estimate Scope

and Purpose Define and document expectations

When all participants understand the scope andpurpose of the estimate, you clear up contradictoryassumptions,

Establish a baseline for measuring the effect of future

changes, and head off potential misunderstandings.

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2-Establish ground rules, and

assumptions To establish an accurate technical baseline, you must

first define the functionality that must be estimated.

Recognize the constraints associated with theapplication and the project.

Determine what functionality must be developed

versus what can be provided via COTS (CommercialOff-the-Shelf )or reuse

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Ground rules are concise statements that describe the

basis from which the estimate is made. No costs associated with travel are included is an

example of a ground rule.

Assumptions are suppositions that describe unknown

variables that will affect an estimate

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2-Establish ground rules, andassumptions


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3-Collect data Identify the data required and the information

holders.

Be sure you are asking the right people the rightquestions.

During interview confirm data is realistic and valid

When you have determined that the supplied data is

valid and complete, publish the corrected raw data. Store the raw and normalized data in a database

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4- Determine size and scope

This is most critical step in determining the ultimatesuccess of a project.

So , spend the bulk of the time you have on sizing theproject .

Use of sizing database and tools can facilitate thisprocess.

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5-Prepare baseline estimate Budget and schedule are derived from estimates.

so if an estimate is not accurate, the resulting

schedules and budgets are likely to be inaccurate also. Estimating a project should not be thought of as a one-

time activity.

As projects progress, unknowns become known's, and

new and unexpected issues and opportunities arise.

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5-Prepare baseline estimate

First, trained, experienced, and skilled people shouldbe assigned to size the software and prepare theestimates.

Second, it is critically important that they be given theproper technology and tools.

And third, the project manager must define and

implement a mature, documented, and repeatableestimation process.

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6-Quantify risks and risk

analysis Risk can be characterized in terms of a loss of time,

quality, money, control, or understanding.

The loss associated with a risk is called the risk impact. Risk cannot be eliminated, but it can be planned for.

Risk, by itself, will not threaten the success of a projectif it is recognized and addressed in a timely fashion.

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7-Validate and reviewValidating and reviewing your estimate provides a

systematic confirmation of your estimates integrity.

This step enables the organization to be moreproactive in adjusting project variables.

and justifies confidence that project data is sound,methods are effective, anticipated results are accurate,

and focus is properly directed. The validation should be performed by someone who

was not involved in generating the estimate itself, whocan view it objectively.

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8-Generate a project plan Generating a project plan employs the project estimate

as a basis for allocating and communicating specificcost, resources, and timelines in a detailed function,

and task-oriented work breakdown structure.

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9-Document estimate and

lessons learned

Each time you complete or update an estimate and

upon completion of a project, you should documentthe information .

Record the lessons you learned.

By doing so, you will have evidence that your process

was valid .

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10-Track performance

(measurement and feedback)

In-process information should be collected

continuously and compared against the original planand baseline.

If performance varies consistently or significantly,corrective options should be evaluated and

implemented to get the project back on track

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Conclusion Software cost estimation is a difficult process but a

necessary part of a successful software development.

Sometimes management is reluctant to take thesesteps(1,6,7)

This can be a costly attitude, because in reality everyshortcut results in dramatic increases in project risks.

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Basic COCOMO is good for quick, early, rough orderof magnitude estimates ofsoftware costs

It does not account for differences in hardwareconstraints, personnel quality and experience, useof modern tools and techniques, and other projectattributes known to have a significant influence onsoftware costs, which limits its accuracy

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The Development Modes: Organic

small" teams

with "good" experience relativelysmall and requires little innovation

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Semidetached Mode

medium" teams.

with mixed experience The size range of a semidetached mode product

generally extends up to 300 KDSI

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Embedded Mode Complex projects where the software is part of a

strongly coupled complex of hardware, software,regulations and operational procedures.

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COCOMO:

Some Assumptions Primary cost driver is the number ofDelivered

Source Instructions (DSI) / Delivered Line OfCode developed by the project

COCOMO estimates assume that the project will enjoygood management by both the developer and the

customer

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Assumes the requirements specification is notsubstantiallychanged after the plans andrequirements phase

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Basic COCOMO Model: FormulaEffort Applied (in person-months) = a* (KLOC)bDevelopment Time (in months) = c * (Effort Applied)dPeople required = Effort Applied / Development Time

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a b c d

Organic 2.4 1.05 2.5 0.38

Semi-detatched 3.0 1.12 2.5 0.35

Embedded 3.6 1.20 2.5 0.32


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Basic COCOMO Model: Equation

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Mode Effort Schedule

Organic E=2.4*(KDSI)1.05 TDEV=2.5*(E)0.38

Semidetached E=3.0*(KDSI)1.12

TDEV=2.5*(E)0.35

Embedded E=3.6*(KDSI)1.20

TDEV=2.5*(E)0.32


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Basic COCOMO Model: ExampleWe have determined our project fits the

characteristics ofSemi-Detached mode

We estimate our project will have32,000 DeliveredSource Instructions. Using the formulas, we canestimate:

Effort = 3.0*(32) 1.12 = 146 Person-months

Schedule = 2.5*(146)0.35

= 14 monthsAverage Staffing = 146 MM /14 months

= 10 FSP

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