CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved CSE7315M11 Slide 1 January 10, 2001 SMU CSE 7315 / NTU SE 584-N Planning and Managing a Software Project Module 11 Overview of Size Estimating

CSE7315M11 Slide # 2 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Objectives of This Module To examine why size estimating is useful To discuss how to measure size To review several categories of estimating methods

CSE7315M11 Slide # 3 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Detailed Planning - Processes Estimate Schedule Evaluate Source Information Statement of Work Requirements Constraints Standards Processes History etc. WBSSize Effort & Cost ScheduleOK Complete Detailed Planning Revise & Negotiate Not OK Estimate Size Estimate Effort and Cost

CSE7315M11 Slide # 4 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Why Do You Need to Estimate the Size? To help you estimate the effort, schedule and cost And to help you estimate the memory requirements, if you need to know them  In theory, you could estimate effort and cost without knowing size – Since you know the tasks to be performed from the WBS, you can (in theory) compute effort and cost directly

CSE7315M11 Slide # 5 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved How To Estimate Cost and Effort Without Estimating Size For each task, you determine effort and then cost, as follows: Task > Effort > Cost This is known as a “bottom up” estimating technique

CSE7315M11 Slide # 6 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved TaskEffortx factorCost staff months$5000/sm$115, staff months$4000/sm$ 20, (3 trips)$1000/trip$ 3, _______________________ Total$435,000 “Bottom Up” Cost Estimating The highlighted tasks are to develop the software. Other tasks are for related activities required by SOW, etc.

CSE7315M11 Slide # 7 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved But Sometimes This is Not So Easy In practice, the software development tasks may be hard to estimate in this fashion It is very hard to estimate the effort to perform a software development task unless you know something about the size and the complexity of the software

CSE7315M11 Slide # 8 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Moreover... Large software projects cost more than small ones; complex software costs more than simple software So you often need to estimate the size and complexity as part of the process of determining the effort required to develop the software

CSE7315M11 Slide # 9 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved In Fact... It may be easier and faster to estimate the effort to do a whole software project than to estimate the exact effort of performing each task Example: -- How long will it take you to answer the questions on the test? vs. -- How long will it take you to answer each individual question?

CSE7315M11 Slide # 10 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved “Short Cut” to Estimate Software Development Effort For Software Development Tasks: use software items rather than tasks: Software ----> Size > Effort > Cost Item & Complexity For Other Tasks: Task > Effort > Cost

CSE7315M11 Slide # 11 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Estimating Software Development Effort SW ItemSizeComplexity File System2400 unitssimple User I/F3000 unitsmoderate ______________ Total35,000 unitsmoderate Historical Data Effort Estimate

CSE7315M11 Slide # 12 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Inputs to Size Estimate What you must do (job analysis) How you will do it (Initial Planning) Past experience and data

CSE7315M11 Slide # 13 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Good job analysis and initial planning will have identified all of these things and summarized them in the work breakdown structure (WBS) “What You Must Do” Inputs Statement of work System design information Requirements of the software Tasks to be Performed

CSE7315M11 Slide # 14 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved “How You Will Do It” Inputs Software items Programming language(s) to be used Initial concepts of software design Process and methods Reusable software information These are also identified during job analysis and initial planning

CSE7315M11 Slide # 15 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved “Past Experience” Inputs Prior experience on similar tasks is valuable in helping you estimate – People who have worked on something similar can be a good source - but they may be biased - or may be unavailable – Historical data can provide useful facts to counteract natural human biases An organizational data base of past project experience is one of the best investments an organization can make

CSE7315M11 Slide # 16 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Past History May Be Particularly Hard to Find Cindy Wilson did that the last time & she left the company last year. We never have time around here to write down what we learned.

CSE7315M11 Slide # 17 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved You May Have to Scramble to Get What Information You Can Hello, Cindy? Can you tell me about how big the user interface module was in project Zing? Hey, George! Who around here knows the most about the HP X123 test station? Anne, can you participate in an estimating session next week? Let’s look at the source code of the old data base module.

CSE7315M11 Slide # 18 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Size Estimating Concept Size Estimate WBS Source Documents (SOW, Requirements, Contract, Test Criteria, etc,) Estimate Size Past Experience & Data

CSE7315M11 Slide # 19 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Size Estimate Step 1 - Determine the Gross Size Estimate Size for Each Distinct SW Item  Gross Size Estimate for All Software Items WBS etc.

CSE7315M11 Slide # 20 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Gross Size Estimate for All Software Items Size (Equivalent) Estimate for All Software Items Size Estimate Step 2 - Evaluate the Impact of Reuse Analyze Impact of Reuse

CSE7315M11 Slide # 21 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Risks of Size Estimating 1) Statistical variance & fundamental inaccuracy of estimating methods – Multiple methods are recommended to increase confidence 2) Biases due to lack of knowledge, optimism, etc. – The earlier in the lifecycle, the less accurate the estimates – Therefore, plan to update estimates when you have more facts

CSE7315M11 Slide # 22 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Accurate estimates are seldom attained, especially early in the lifecycle – Early estimates tend to be underestimates The goal of estimating is – to help plan the project – to educate estimators – to manage risk Warning -- Estimate = Goal You don’t need a perfect prediction to manage a project effectively

CSE7315M11 Slide # 23 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Units of Size

CSE7315M11 Slide # 24 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Important Questions What unit will you use to measure size? – It should be related to effort How will you define it? – Everyone should be measuring the same thing How will you measure it? – Can you measure it accurately? – Can you measure it easily?

CSE7315M11 Slide # 25 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved The decision about which unit is best should be based on the suitability of a unit to your application domain Some Possible Units of Size Lines of Code – Which ones count? – Do comments count? Functions performed Objects in the design Required bytes of computer memory Number of requirements

CSE7315M11 Slide # 26 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved How to Decide Between Options? Is data available to help you estimate? – previous, similar projects are best Is your unit of measure suited to the application & your organization’s processes? How easy is it to measure? Consistency between projects is more important than the measure itself.

CSE7315M11 Slide # 27 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Keep the Goal in Mind The goal is to help you estimate effort and memory size The goal is not to have the most precise and perfect unit for measuring size – Don’t get hung up in debates about what unit to measure – If it works, use it

CSE7315M11 Slide # 28 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved How to Define a Unit - Example - What Is a Line of Code? Source line images? – 80 characters/carriage return character Source statements? – Semicolons (in some languages) Do comments count? (usually not) Data Declarations? (usually yes)

CSE7315M11 Slide # 29 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Notes Most methods of size estimating will work with just about any size unit you choose We will illustrate the process with “lines of code”, and will later discuss other units

CSE7315M11 Slide # 30 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Estimating Methods and Models Note: Except where noted, these methods can be used for estimating size OR effort.

CSE7315M11 Slide # 31 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved 1. Analogy Models – Compare with past experience History is a good ally – But truly similar models seldom exist – Use as a baseline for “sanity” checks or when no other method is available Categories of Estimating Methods Stukes, Sherry, “A Guide to Cost Estimation for Space Systems Software,” Management Consulting and Research, 1995/1999

CSE7315M11 Slide # 32 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved 2. Expert Judgment Models – Consult with experts Examples: Hire a consultant Wideband Delphi – Good for new, unique & different situations – High risk of biased/insufficient knowledge – Use in conjunction with other models Categories of Estimating Methods (continued)

CSE7315M11 Slide # 33 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved 3. Prototyping – Build a model of the parts that are riskiest or least well understood Prototypes take time – But they can answer questions raised by other estimating methods Categories of Estimating Methods (continued)

CSE7315M11 Slide # 34 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved 4. Bottom-up Models – Estimate each component – And add them all up Expensive and time consuming, but – Good for tracking costs later – “Buy-in” from developers – Use if data and time are available – Won’t work if you lack key information – Ignores integration/support Categories of Estimating Methods (continued)

CSE7315M11 Slide # 35 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Categories of Estimating Methods (continued) 5. Top-Down Models – Estimate based on general characteristics of application, environment, personnel, etc. – Normally these are used for effort, not size Examples: Cocomo, Price-S, SEER, etc. – Fast, easy to use, requires little detail, captures system costs – Less accurate and stable than bottom-up – Does not foster buy-in to estimate – Use - but calibrate to your own data

CSE7315M11 Slide # 36 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Architecture of Spreadsheet for assignments 3 and 4 Cocomo Based Effort Estimate Other Effort Estimates... Analogy based Size Estimate Software Reuse Analysis Size / Reuse EffortEffort & Cost Schedules Final Effort Estimate Productivity Based Effort Estimate Generic Schedule Effort Schedule Labor Schedule Cost Schedule Other Size Estimates... Final Size Estimate Expert Based Size Estimate

CSE7315M11 Slide # 37 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Architecture of Spreadsheet for assignments 3 and 4 Cocomo Based Effort Estimate Other Effort Estimates... Analogy based Size Estimate Software Reuse Analysis Size / Reuse EffortEffort & Cost Schedules Final Effort Estimate Productivity Based Effort Estimate Generic Schedule Effort Schedule Labor Schedule Cost Schedule Other Size Estimates... Final Size Estimate Expert Based Size Estimate This diagram serves as a guide to the next several modules

CSE7315M11 Slide # 38 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved Module Summary Size estimates help you estimate effort and memory size They can also be helpful for tracking (this will be shown in later modules) Most estimating methods benefit from past experience or history data Units of size should be chosen based on availability of data in those units

CSE7315M11 Slide # 39 January 10, 2001 CSE SW Project Management / Module 11 - Overview of Size Estimating Copyright © , Dennis J. Frailey, All Rights Reserved END OF MODULE 11