EFFORT ESTIMATION

EFFORT ESTIMATIONRISK MANAGEMENTTotal time required by the project to get completed.The overall cost of the project.EFM is generally viewed as function whose output will be the effort required accomplishing the project.Function needs inputInput will be characteristics of the project.E.g. Size of the project.EFFORT = a*SIZE^bWhere a and b are some constants and SIZE is the project in terms of KLOC.According to Watson and Felixs observation of more than 60 projects, they estimated value of a and b are :EFFORT = 5.2*SIZE^0.91Unit of EFFORT is Person-Months.Productivity = KLOC/PMThis approach is TOP DOWN APPROACHBecause we compute the size of the projectDisadvantage : Based on size.If size estimation is inaccurate, then the effort estimation will be wrong.BOTTOM UP APPROACHProject is partitioned into small tasks.Effort is then calculated for these tasks.Easy to calculate and estimate.Disadvantage : Some times there are chances of omitting some of the activities.COCOMO MODELConstructive Cost Model (COCOMO)Developed by BoehmA model for estimating effort, cost, and schedule for software projects3 DIFFERENT MODELS OF COCOMOBasic COCOMOIntermediate COCOMOsDetailed COCOMO

3 DIFFERENT CLASSES OF PROJECTSOrganic projects - "small" teams with "good" experience working with "less than rigid" requirementsSemi-detached projects - "medium" teams with mixed experience working with a mix of rigid and less than rigid requirementsEmbedded projects - developed within a set of "tight" constraints. It is also combination of organic and semi-detached projects.(hardware, software, operational, ...)

BASIC COCOMO MODELThe basic COCOMO equations takeS the formEffort Applied (E) = ab(KLOC)bb [ man-months ] Development Time (D) = cb(Effort Applied)db [months] People required (P) = Effort Applied / Development Time [count] where, KLOC is the estimated number of delivered lines (expressed in thousands ) of code for project. The coefficients ab, bb, cb and db are given in the following table:BASIC COCOMO MODEL

Advantages of basic COCOMOBasic COCOMO model is good in quick and early estimation of software project costs.Advantages AND DisadvantagesAdv : Basic COCOMO model is good in quick and early estimation of software project costs.Disadv : The basic COCOMO Model is limited in functionality because it doesn't consider certain factors of cost estimation such as hardware constraints, personnel quality and experience and modern techniques and tools.exampleConsider a software project using semi-detached mode with 30,000 lines of code. Obtain the estimation for this project.1. Effort Estimation : 2. Duration Estimation3. Persons EstimationIntermediate COCOMOscomputes software development effort as function of program size and a set of "cost drivers" that include subjective assessment of product, hardware, personnel and project attributes.Cost drivers are : Product attributes Hardware attributes Personnel attributes Project attributes Product AttributesRequired software reliabilitySize of application databaseComplexity of the product

Hardware AttributesRun-time performance constraintsMemory constraintsVolatility of the virtual machine environmentRequired turnabout time

Personnel attributes Analyst capabilitySoftware engineering capabilityApplications experienceVirtual machine experienceProgramming language experience

Project AttributesUse of software toolsApplication of software engineering methodsRequired development scheduleAttribute RatingEach of the 15 attributes receives a rating on a six-point scale that ranges from "very low" to "extra high" (in importance or value). An effort multiplier from the table below applies to the rating. The product of all effort multipliers results in an effort adjustment factor (EAF). Typical values for EAF range from 0.9 to 1.4.

Ratings

The Intermediate Cocomo formula now takes the form:E=ai(KLoC)(bi).EAF Person MonthsWhere E = Effort in PMKLOC is the no. of lines in thousandsEAF = Effort Adjustment FactorAnd the values of coefficients ai , bi

Note : The Development time D calculation uses E in the same way as in the Basic COCOMO.Note : The Development time D calculation uses E in the same way as in the Basic COCOMO.Advantages and DisadvantagesAdvantages : Can be applied to almost entire software project for easy and rough implementation during early stages.for obtaining more accurate cost estimation.Disadvantages : A Product with many components is difficult to estimate with Intermediate COCOMO.effort multipliers are not dependent on phase.ExampleConsider a project having 30KLOC which is an embedded software with critical area hence reliability is high. Estimate E, D and P.

E = 191 PMD = 13 monthsP = 15 Persons (approx)Detailed COCOMOincorporates all characteristics of the intermediate version with an assessment of the cost driver's impact on each step (analysis, design, etc.) of the software engineering process.uses different effort multipliers for each cost driver attribute.effort is calculated as function of program size and a set of cost drivers5 Phases of Detailed COCOMOplan and requirement.system design.detailed design.module code and test.integration and test.

Advantages and DisadvantagesTransparent -> One can see how it works.One can understand the impact of different factors that affect the project costs.

Disadvantages :Success of this model depends largely on tuning the model to the needs of organization.It is extremely vulnerable to mis-classification of the development mode.

Chapter 25

Risk Management

Introduction Risk identification Risk projection (estimation) Risk mitigation, monitoring, and management (Source: Pressman, R. Software Engineering: A Practitioners Approach. McGraw-Hill, 2005)Introduction34Definition of RiskA risk is a potential problem it might happen and it might notConceptual definition of riskRisk concerns future happeningsRisk involves change in mind, opinion, actions, places, etc.Risk involves choice and the uncertainty that choice entailsTwo characteristics of riskUncertainty the risk may or may not happen, that is, there are no 100% risks (those, instead, are called constraints)Loss the risk becomes a reality and unwanted consequences or losses occur

35Risk Categorization Approach #1Project risks They threaten the project planIf they become real, it is likely that the project schedule will slip and that costs will increaseTechnical risks They threaten the quality and timeliness of the software to be producedIf they become real, implementation may become difficult or impossibleBusiness risks They threaten the viability of the software to be builtIf they become real, they jeopardize the project or the product

(More on next slide)36Risk Categorization Approach #1 (continued)Sub-categories of Business risks Market risk building an excellent product or system that no one really wantsStrategic risk building a product that no longer fits into the overall business strategy for the companySales risk building a product that the sales force doesn't understand how to sellManagement risk losing the support of senior management due to a change in focus or a change in peopleBudget risk losing budgetary or personnel commitment

37Risk Categorization Approach #2Known risksThose risks that can be uncovered after careful evaluation of the project plan, the business and technical environment in which the project is being developed, and other reliable information sources (e.g., unrealistic delivery date)Predictable risksThose risks that are extrapolated from past project experience (e.g., past turnover)Unpredictable risksThose risks that can and do occur, but are extremely difficult to identify in advance

38Reactive vs. Proactive Risk StrategiesReactive risk strategies"Don't worry, I'll think of something"The majority of software teams and managers rely on this approachNothing is done about risks until something goes wrongThe team then flies into action in an attempt to correct the problem rapidly (fire fighting)Crisis management is the choice of management techniquesProactive risk strategiesSteps for risk management are followed (see next slide)Primary objective is to avoid risk and to have a contingency plan in place to handle unavoidable risks in a controlled and effective manner

39Steps for Risk ManagementIdentify possible risks; recognize what can go wrongAnalyze each risk to estimate the probability that it will occur and the impact (i.e., damage) that it will do if it does occurRank the risks by probability and impact - Impact may be negligible, marginal, critical, and catastrophicDevelop a contingency plan to manage those risks having high probability and high impactRisk Identification41BackgroundRisk identification is a systematic attempt to specify threats to the project planBy identifying known and predictable risks, the project manager takes a first step toward avoiding them when possible and controlling them when necessaryGeneric risks Risks that are a potential threat to every software projectProduct-specific risks Risks that can be identified only by those a with a clear understanding of the technology, the people, and the environment that is specific to the software that is to be builtThis requires examination of the project plan and the statement of scope"What special characteristics of this product may threaten our project plan?"42Risk Item ChecklistUsed as one way to identify risksFocuses on known and predictable risks in specific subcategories (see next slide)Can be organized in several waysA list of characteristics relevant to each risk subcategory Questionnaire that leads to an estimate on the impact of each riskA list containing a set of risk component and drivers and their probability of occurrence

43Known and Predictable Risk CategoriesProduct size risks associated with overall size of the software to be builtBusiness impact risks associated with constraints imposed by management or the marketplaceCustomer characteristics risks associated with sophistication of the customer and the developer's ability to communicate with the customer in a timely mannerProcess definition risks associated with the degree to which the software process has been defined and is followedDevelopment environment risks associated with availability and quality of the tools to be used to build the projectTechnology to be built risks associated with complexity of the system to be built and the "newness" of the technology in the systemStaff size and experience risks associated with overall technical and project experience of the software engineers who will do the work44Questionnaire on Project RiskHave top software and customer managers formally committed to support the project?Are end-users enthusiastically committed to the project and the system/product to be built?Are requirements fully understood by the software engineering team and its customers?Have customers been involved fully in the definition of requirements?Do end-users have realistic expectations?Is the project scope stable?

(Questions are ordered by their relative importance to project success)(More on next slide)45Questionnaire on Project Risk (continued)Does the software engineering team have the right mix of skills?Are project requirements stable?Does the project team have experience with the technology to be implemented?Is the number of people on the project team adequate to do the job?Do all customer/user constituencies agree on the importance of the project and on the requirements for the system/product to be built?46Risk Components and DriversThe project manager identifies the risk drivers that affect the following risk componentsPerformance risk - the degree of uncertainty that the product will meet its requirements and be fit for its intended useCost risk - the degree of uncertainty that the project budget will be maintainedSupport risk - the degree of uncertainty that the resultant software will be easy to correct, adapt, and enhanceSchedule risk - the degree of uncertainty that the project schedule will be maintained and that the product will be delivered on timeThe impact of each risk driver on the risk component is divided into one of four impact levelsNegligible, marginal, critical, and catastrophicRisk drivers can be assessed as impossible, improbable, probable, and frequent

Risk Projection (Estimation)48BackgroundRisk projection (or estimation) attempts to rate each risk in two waysThe probability that the risk is realThe consequence of the problems associated with the risk, should it occurThe project planner, managers, and technical staff perform four risk projection steps (see next slide)The intent of these steps is to consider risks in a manner that leads to prioritizationBe prioritizing risks, the software team can allocate limited resources where they will have the most impact

49Risk Projection/Estimation StepsEstablish a scale that reflects the perceived likelihood of a risk (e.g., 1-low, 10-high)Delineate the consequences of the riskEstimate the impact of the risk on the project and productNote the overall accuracy of the risk projection so that there will be no misunderstandings50Contents of a Risk TableA risk table provides a project manager with a simple technique for risk projectionIt consists of five columnsRisk Summary short description of the riskRisk Category one of seven risk categories (slide 12)Probability estimation of risk occurrence based on group inputImpact (1) catastrophic (2) critical (3) marginal (4) negligibleRMMM Pointer to a paragraph in the Risk Mitigation, Monitoring, and Management Plan

Risk SummaryRisk CategoryProbabilityImpact (1-4)RMMM(More on next slide)51Developing a Risk TableList all risks in the first column (by way of the help of the risk item checklists)Mark the category of each riskEstimate the probability of each risk occurringAssess the impact of each risk based on an averaging of the four risk components to determine an overall impact value (See next slide)Sort the rows by probability and impact in descending orderDraw a horizontal cutoff line in the table that indicates the risks that will be given further attention

52Assessing Risk ImpactThree factors affect the consequences that are likely if a risk does occurIts nature This indicates the problems that are likely if the risk occursIts scope This combines the severity of the risk (how serious was it) with its overall distribution (how much was affected) Its timing This considers when and for how long the impact will be feltThe overall risk exposure formula is RE = P x CP = the probability of occurrence for a riskC = the cost to the project should the risk actually occurExampleP = 80% probability that 18 of 60 software components will have to be developedC = Total cost of developing 18 components is $25,000RE = .80 x $25,000 = $20,000Risk Mitigation, Monitoring, and Management54BackgroundAn effective strategy for dealing with risk must consider three issues (Note: these are not mutually exclusive)Risk mitigation (i.e., avoidance)Risk monitoringRisk management and contingency planningRisk mitigation (avoidance) is the primary strategy and is achieved through a planExample: Risk of high staff turnover (see next slide)(More on next slide)55Meet with current staff to determine causes for turnover (e.g., poor working conditions, low pay, competitive job market)Mitigate those causes that are under our control before the project startsOnce the project commences, assume turnover will occur and develop techniques to ensure continuity when people leaveOrganize project teams so that information about each development activity is widely dispersedDefine documentation standards and establish mechanisms to ensure that documents are developed in a timely mannerConduct peer reviews of all work (so that more than one person is "up to speed")Assign a backup staff member for every critical technologistStrategy for Reducing Staff TurnoverBackground (continued)56Background (continued)During risk monitoring, the project manager monitors factors that may provide an indication of whether a risk is becoming more or less likely Risk management and contingency planning assume that mitigation efforts have failed and that the risk has become a realityRMMM steps incur additional project costLarge projects may have identified 30 40 risksRisk is not limited to the software project itselfRisks can occur after the software has been delivered to the user(More on next slide)57Background (continued)Software safety and hazard analysisThese are software quality assurance activities that focus on the identification and assessment of potential hazards that may affect software negatively and cause an entire system to failIf hazards can be identified early in the software process, software design features can be specified that will either eliminate or control potential hazards58The RMMM PlanThe RMMM plan may be a part of the software development plan (Paragraph 5.19.1) or may be a separate documentOnce RMMM has been documented and the project has begun, the risk mitigation, and monitoring steps beginRisk mitigation is a problem avoidance activityRisk monitoring is a project tracking activityRisk monitoring has three objectivesTo assess whether predicted risks do, in fact, occurTo ensure that risk aversion steps defined for the risk are being properly appliedTo collect information that can be used for future risk analysisThe findings from risk monitoring may allow the project manager to ascertain what risks caused which problems throughout the project59Seven Principles of Risk ManagementMaintain a global perspectiveView software risks within the context of a system and the business problem that is is intended to solveTake a forward-looking viewThink about risks that may arise in the future; establish contingency plansEncourage open communicationEncourage all stakeholders and users to point out risks at any timeIntegrate risk managementIntegrate the consideration of risk into the software processEmphasize a continuous process of risk managementModify identified risks as more becomes known and add new risks as better insight is achievedDevelop a shared product visionA shared vision by all stakeholders facilitates better risk identification and assessmentEncourage teamwork when managing riskPool the skills and experience of all stakeholders when conducting risk management activities60SummaryWhenever much is riding on a software project, common sense dictates risk analysisYet, most project managers do it informally and superficially, if at allHowever, the time spent in risk management results inLess upheaval during the projectA greater ability to track and control a projectThe confidence that comes with planning for problems before they occurRisk management can absorb a significant amount of the project planning effortbut the effort is worth it