the journal of aace® international - costhe …... engineeringengineering march/april 2016 the...

www.aacei.orgENGINEERINGENGINEERING

March/April 2016

THE JOURNAL OF AACE® INTERNATIONAL -THE AUTHORITY FOR TOTAL COST MANAGEMENT®

COSTCOSTTHE PLANNING FALLACYAND ITS EFFECT ON REALISTICPROJECT SCHEDULES

FORENSIC SCHEDULE ANALYSISAND DISCRETIONARY LOGIC

REVIEWING RESOURCE LEVELED SCHEDULES USING P6TM

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21COST ENGINEERING MARCH/APRIL 2016

“H ow long do youthink that task willtake?” Anyone whohas participated in a

planning discussion to lay out a proj-ect’s schedule will recognize this fun-damental question asked to projectteam members. It often initiates an un-settling pause while the person respon-sible for the task contemplates the“correct” answer. Frequently, the an-swer is a gross underestimation of theactual duration needed to completethe task. When these individual, short-ened task durations are linked to formthe full project schedule, the result isoften a misrepresentation of the timeneeded to complete the overall project.

This tendency to underestimatetask durations is commonly referred toas the planning fallacy [2]. Theories onwhy this effect occurs tend to focus

more on psychological research thanon traditional project managementissues. As an experienced projectmanager or planner, it is important torecognize when this effect is occurringand make adjustments during thedevelopment of the schedule. Thisarticle explores common reasons forthe planning fallacy, provides insighton typical situations where it occurs,and offers techniques to help developmore realistic project schedules.

The Planning Fallacy DefinedThe planning fallacy concept was

first used by Daniel Kahneman andAmos Tversky to describe thetendency to underestimate the timeneeded to complete a given task.More importantly, they found that thisunderestimation happens even whenpeople have previous experience in

performing similar tasks. Kahnemanstates that the planning fallacydescribes plans and forecasts that:

• Are unrealistically close to best-case scenarios

• Could be improved by consultingthe statistics of similar cases [7].

Kahneman also describes theexercise that first led him to describethe concept. He was working with ateam of colleagues to write anacademic textbook. After progressingfor about a year, he asked each teammember to independently write downhow long they thought it would take tofinish a draft of the book. Theestimates generally centered aroundtwo more years, with a range of oneand a half to two and a half years.

He then asked one colleague whohad extensive experience with otheracademic textbooks how much longerit had taken similar teams to finish adraft, once they had reached the samepoint in development. Theexperienced colleague gave thisquestion additional thought anddelivered some bad news: it typicallytook about seven more years to finish.Even worse — about 40 percent of theother teams never finished their booksat all.

Kahneman’s textbook team wasshocked to hear the actual timeframesof similar projects. The team could not

The Planning Fallacyand Its Effect on Realistic Project SchedulesJeffrey Valdahl and Shannon A. Katt

Abstract: “How long do you think that task will take?” It’s a question that isasked frequently during the course of a project, but is often answered withlittle or no factual basis. Project team members typically underestimate thetime needed to complete a task they are responsible for. This tendency hasbeen referred to as the “planning fallacy,” and it can have a dramatic effecton developing a realistic overall project schedule. This article examines var-ious causes of the planning fallacy, including optimism bias, lack of task un-packing, and short memory. As a project manager or planner, it is important to recognize when thesepsychological effects are impacting your project schedule. This article usesexamples from various projects to show where this challenging planningissue is likely to occur. Identifying where adjustments need to be made, atboth the task and overall project level, is essential in developing a projectschedule that is both achievable and reasonable.

TECHNICAL ARTICLE

22 COST ENGINEERING MARCH/APRIL 2016

imagine what might take them thatlong, so they promptly noted thecomparables but stuck with theiroriginal duration estimate. Kahnemanstates that his team had committed aplanning fallacy by relying on internalestimates that, “were closer to a best-case scenario than to a realisticassessment.” The textbook ended uptaking eight more years to complete!

Research on the planning fallacyhas been conducted primarily in thearea of psychology, rather than inproject management. The variousresearch areas include the effects ofdeadlines, perceived durations ofsimilar previous tasks, level ofplanning detail, anchored dates,individual versus group planning,egos, team power structure, and bias.From that research, some methodshave been developed that try andoffset potential effects of the planningfallacy.

Recognizing the Planning FallacyA savvy project manager or

planner will recognize when theirproject team is becoming aggressivein their activity duration estimates.Often, recognition happens whenactivity sequences or project phasesappear to be forced into time framesestablished by top-down planningtechniques. In other cases, anunrealistic project schedule is theoutput of a collaborative planningsession driven by a few influentialteam members. These situations needto be recognized during the planningprocess and then offset withchallenges to the basis of optimisticdurations. Frequently, the personquestioning the validity of theplanned schedule is not very popularwith the rest of the group [1].

The following sections describeproject schedule planning situationsthat often promote planning fallacyeffects. Identifying when these occuris a key to offsetting them and todeveloping a more realistic overallproject schedule.

The Project Planning Environment

When project schedules aredeveloped in a group environment,gathering project team members in aconference room to walk throughtheir assigned tasks in the context ofthe entire project is a commonapproach. Various tools are used toplan the project, from sticky notes tospecialized software that facilitates agroup collaboration effort. A projectplan and schedule that the full projectteam “buys into” are the measure ofsuccess.

Unfortunately, research suggeststhat this group planning environmentoften exacerbates planning fallacyissues. Group predictions tend to bemore optimistic than those set by anindividual. Researchers havedescribed this group accentuationeffect as a result of dynamics betweenteam members during the planningprocess. Even though individualmembers can act as observers toother members’ tasks, anyimpartiality tends to beovershadowed by being an activeparticipant and stakeholder to theentire group’s optimism [3].

To examine various groupplanning scenarios that lead to theplanning fallacy and overly optimisticproject schedules, we will visit aplanning meeting for the fictitious YYZPlant Expansion Project.

Project Team Optimism Bias

• YYZ Project Director: “Two years is more than enough

time to design and construct theexpansion project.”

• Construction Manager:“Absolutely. If you get me thedesign and major deliveries by thebeginning of the year, we willhave it up and running by theholidays.”

• YYZ Operations Manager:“Remember we ran into someproblems when the previous unitwas started up.

• YYZ Project Manager: “Yeah, but those were caused by

our equipment vendors, not us.We will just source our equipmentfrom another vendor”

This is an example of groupoptimism bias. Both individuals andgroups often attribute past successesto themselves but failures to outsidefactors [14]. Typical thinking is thatproblems that happened last timewere one-offs and will not happenagain. There is always a chance thatthe new project will have valid lessonslearned from previous efforts, butcomplications that happened beforemust be recognized [8].

Projects planned backward froma desired end date can exhibit thisgroup bias. Activities frequently getshoe-horned into desired time framesand have unrealistically shortdurations. Even though schedules aremost often easier to develop “whenyou know the answer first,” projectteams should be cautious whenplanning activities to meet interimdate benchmarks. Projects frequentlyhave hard completion dates (e.g., theOlympics), but their activities arealways executed in the forwarddirection from the start, regardless ofhow they were planned. Unrealistic,backward-planned durations can leadlater on to sacrifices in scope, cost, orquality to meet deadlines that mayhave been established without a solidbasis.

The project environment alsotends to produce an inherent bias byteam members. There is a strongdesire to keep the project movingforward at all times, with requiredapprovals and funding. This bias canlead to overly aggressive schedules forthe next phase of the project in orderto comply with economic andoperational targets establishedoutside of the project [2]. No one whoworks in the projects business enjoysthe uncertain period betweenassignments, especially after a projectgets cancelled. Terminating a projectbefore it is completed is often acorrect decision, but schedule bias


from those directly involved in theproject can cloud an impartial projectevaluation.

Team Member Egos

• YYZ Project Director: “Some of the higher-ups are

saying there is no way the plantexpansion construction can bedone in a year.”

• YYZ Construction Manager:“We will make it happen. I havenever missed a deadline on one ofmy projects and I am not going tostart now.”

• YYZ Project Manager: “I just want to make sure we do

not promise to meet the end ofthe year deadline and then notdeliver.”

• YYZ Construction Manager:“Look, I am not going to havesomebody from the corporateoffice telling me how long it willtake to get my constructiondone.”

Nobody likes to have their abilityto perform on a project questioned,especially by someone outside of theproject. Protecting egos and self-esteem is a common occurrence inbusiness and in a high-pressureproject environment [14]. “Ifeveryone else would just get us whatwe need and then stay out of our way,we could get our tasks done when wesay they are going to be done.” Anydelays that occur are often blamed onsomeone else, or on factors outside ofa team member’s control.

Unfortunately, this individualoptimism brought on by teammember egos can lead to a veryaggressive schedule when all tasks arecombined. All of the optimistic teammembers must deliver on ego-drivenpromises for the project schedule tostay on track. When the inevitabledelay occurs, the unrealistic projectschedule is exposed, and frequently,finger-pointing begins.

Schedule Anchors

• YYZ Engineering Manager:“So our current engineeringschedule shows that all detaileddrawings will be issued by the endof April.”

• YYZ Project Sponsor: “Wait. In the approved funding

document we said that we wouldhave engineering done fourmonths earlier in December.”

• YYZ Project Manager: “Yeah, but we added more

equipment scope and are stillwaiting on vendor drawings, sothat is adding time toengineering.”

• YYZ Project Director: “Well, we originally told the

Board the end of December forengineering completion. Unlessyou two want to stand in front ofthem and explain why we cannotmake it, we need to make ithappen.”

Specific dates tend to establishthemselves in project stakeholders’minds. Research in this area suggeststhat when quantities and overallscope of a project are still notestablished, people are still relativelycomfortable in estimating a project’scompletion date [10]. These initialestimates, even though often withouta firm basis, are often “anchored” tothe project and to its stakeholdersgoing forward.

Even when new information, oradditional scope, suggests that thecompletion date should be extended,stakeholders often are anchored tothe original date and are reluctant tochange [8]. If the original anchoreddate is based on a biased prediction,any adjustments made to reflectspecific project information willusually still result in an unreasonablerevised date [12].

Power Bias

• YYZ Team Member: “After we receive all the vendor

information, it will take our

modeling department eightweeks to complete the modelbefore we can have a review”

• YYZ Project Director: “Eight weeks???”• YYZ Team Member: “Yes. This is a pretty complex

model, especially for the newexpansion pipe routing. It willtake a solid eight weeks to resolveclashes and finalize the model.”

• YYZ Project Director: “Well, we do not have eight

weeks. Let us put four in theschedule. Are you OK with that?”

• YYZ Team Member: “Um, I guess so.”• YYZ Project Director: “Good, four weeks it is.”

Power and intimidation canbecome a major factor in groupschedule planning sessions. If aparticipant has legitimate power oversubordinates on the project team,that high-ranking individual candominate activity durationdiscussions. Studies show that groupscontaining a powerful memberconsistently led to more optimisticand less accurate time predictions[15]. This power influence leads to aselective focus on a dominant, goal-focused opinion with less focus onoften-relevant, secondary information.

An effective planning facilitatorwill recognize when this situation isoccurring and try to coax additionalopinions from other intimidated teammembers; this can be quite achallenge in a group environment.Sometimes a “divide-and-conquer”approach is effective where smaller,similar-level groups are assembled toobtain schedule information frommultiple sources, which is thenintegrated later.

Short Memory

• YYZ Construction Manager:“We have three months in ourschedule to construct thefoundations for the newexpansion equipment.”


• YYZ Project Planner: “Three months seems pretty

short. When we did thefoundations for the previousexpansion project during thewinter months, it took a prettylong time. ”

• YYZ Construction Manager: “I remember, but there is no way

it was much longer than what weare showing.”

• YYZ Project Manager: “Can you pull up the schedule

from the last expansion projectand look up how long it took?”

• YYZ Project Planner: “Here it is. Wow! It took us about

five and a half months until wewere done with the foundations.”

• YYZ Construction Manager:“That cannot be right, and we willhave better weather this winter. Iam going to stick with my threemonths.”

How long did the previous projecttake to perform the same sequence oftasks? Project managers and eventeam members that performed thework prior have a tough timeaccurately remembering how long ittook to complete past activities. This“memory bias” has been studiedextensively in conjunction withplanning fallacy. These incorrectmemories of past task durations are amajor cause of biased futurepredictions [11, 12].

Vierordt’s Law (1868) says thatshort intervals of time tend to beoverestimated, while long periods oftime are typically underestimated.This effect can lead to incorrectapproximations of the actualdurations on past projects or phases.Additional studies show thatproviding people with the accurateactual duration of past tasks improvedtheir prediction accuracy of futuresimilar tasks [13]. However, planningfallacy effects can still play a rolewhen historical information isdiscounted or ignored [8].

A key factor in overcoming thismemory bias is the availability ofaccurate, past project schedule

information. A collection ofcompleted, “as-built” projectschedule information should be apriority for project organizations. As-built activity records could evolve intoa statistical distribution of actualdurations from which various activitydurations that best correlate to thecurrent project parameters may beselected. Three-point durationestimates (optimistic/mostlikely/pessimistic) could also bereferenced for schedule risk analysis.This approach to mitigating theplanning fallacy is a forecastingmethod advocated by Bent Flyvjberg[4].

Task Unpacking

• YYZ Project Manager: “Let us put two months in the

planned schedule for reviews andapprovals before full-fundingapproval.”

• YYZ Project Planner: “I am not sure the standard two-

month rule-of-thumb is enoughanymore.”

• YYZ Controls Manager:“Do we know all the requiredstage gate reviews and approvalsthat we need to go through underthe new project process?”

• YYZ Project Director: “I know we are supposed to have

external reviews for both cost andschedule. I think there is going tobe an internal project audit too,but I am not sure if it has beenfinalized yet.”

• YYZ Project Manager: “Well, if they really want this

project to meet the end of theyear deadline, we cannot takemore than two months to getfunding.”

• YYZ Controls Manager:“Let us try and lay out all therequired steps once we find outeverything we need to do.”

Three Weeks Later…

• YYZ Project Planner:

“I came up with a timeline for theeight separate reviews andapprovals we need to get. Withthe holidays falling right in themiddle, it looks like it is going totake at least four months fromstart to finish ― and that is if allthe external reviewers areavailable when we need them.”

• YYZ Project Manager: “That is unbelievable! Looks like I

need to put in for some advancedfunding to keep this projectmoving forward.”

The level of detail in a project’splanned schedule can have an effecton its overall duration. Research inthis area has focused on the “taskunpacking” scenario where longeractivities are broken down into moredetailed, shorter-duration tasks.Results show that when this taskunpacking is incorporated to moreaccurately reflect the sequence ofsteps needed to complete thesummary activity, the total estimatedduration is typically increased [6].Interestingly, near-term activities thatare unpacked normally have theirdurations increased more thanactivities that are further in thefuture. This suggests that people canfocus more easily on developingdetailed task sequences whenrequirements have been set forperforming upcoming work.

The average project manager orplanner might react to this researchby requiring extremely detailedschedules for projects to obtain amore accurate (and often longer)overall duration. But development oflarge, detailed schedules for projectsalso takes extended time andresources. Finding the level-of-detail“sweet spot” where sufficientbreakdown exists for the critical pathor key sequences, while maintainingreasonable development time, can bedifficult. Task unpacking researchsuggests that a better approach couldbe a rolling wave of scheduledevelopment with more detail fornear-term work and summary-levelactivities for work in the future.


Combating the Planning FallacyThe planning fallacy is a real

psychological phenomenon thatrequires a focused effort to offset itseffect. Discussed here are a few of themany suggested options for makingthat happen.

Inside vs. Outside View and High-Level Sanity Check

The inside view relates to theperspective of project participantswho draw from their own personalknowledge and experience. Incontrast, the outside view draws fromexternal sources of information [5]. Ithas been found that using feedbackfrom other similar projects (outsideview) will lead you to a more realisticschedule [13] than the inside view,which tends to be clouded by aninability to see one’s ownshortcomings. Whenever possible,you should strive to obtain externaldata for similar projects to provideunbiased information.

Figure 1 shows an example of ahigh-level metric comparisonbetween construction duration andlabor hours. Similar metrics can beused to validate the current plan

against the durations of comparablepast projects.

Ordinal DatesProject team members have a

tendency to fixate on a calendar date,often anchoring to it, as discussedpreviously. They have predisposedideas of when they expect to performvarious phases of the project and willadjust durations to make that happen,even if those durations conflict with

reality. This is particularly commonwhen activities are weather-sensitiveand the desire is to perform that workduring the summer months. Tocombat this tendency, it is oftenuseful to set the calendar strip of theschedule to ordinal number dates asdepicted in Figure 2.

Seeing that concrete work isplanned for month three does notenlist the same reaction as concretework planned for January. Once the

Figure 1 – Example Schedule Metric (Construction Duration vs. Labor Hours)

Figure 2 – Example Schedule with Ordinal Dates

ordinal calendar is converted tonamed calendar periods, someseasonality duration adjustments maybe required for potential weather-impacted work.

The Pre-MortemAnother helpful tool for getting

project participants to accept thatunplanned things do happen is to havea pre-mortem discussion [9]. A pre-mortem assumes that you are at theend of a project and you havecompleted late. Looking back, whatwere the things that were likely tohave caused the delay? Did you notproperly assess risks that impactedthe schedule, like late equipmentdelivery, or possibly were you overlyoptimistic in your labor productivity?Maybe you assumed you would getfunding at a particular time and it wasdelayed. A focused effort to identifyproject risks at the beginning willfacilitate mitigating those risks oravoiding them completely.

ResourceOverpromising/AwarenessSchedules are often developed

with no consideration to the resourcesneeded to complete the plan.Reviewing the resource requirementsagainst the schedule will enable areview of what the labor requirementswill be. Are they reasonable? Or arethe durations so optimistic versus theestimated labor hours that moreworkers are required than canphysically work in the area? Are therepeaks in the resource profile that canbe smoothed if a more realistic(longer) duration is set, particularly foractivities not on the critical path?

“Risked” SchedulesLinking a pre-mortem with a

Coach’s Challenge (see explanationlater in this article) is the process ofperforming a risk analysis on theproject schedule. A probabilisticschedule risk analysis reviews thedurations set by the project team andquestions them. For each activityreviewed, the group determines theoptimistic, pessimistic, and most likely

durations. The schedule is thenanalyzed in a Monte-Carlo typesimulation using those low/high/mostlikely durations. The result is a set ofprobabilistic durations for the overallschedule. A thorough analysis willattempt to remove inherent biases inthe base schedule and replace themwith more realistic, optimistic, andpessimistic cases.

The result is often a completiondate far beyond that of the projectplan and one that is difficult to accept[1]. In fact, an achievable deterministictarget schedule is rare even in afraction of analyses simulations. Thereare several significant benefits toperforming a risk analysis on theproject schedule, in addition to theoutput of an actual probabilisticanalysis.

First, the analysis itself forces theteam to take a close look at thedurations and confirm their validity. Inmany cases, the team realizes thatthey have been too optimistic in theirplanning and will adjust durations to amore reasonable length. A third-partyfacilitator, however, can get the teamto focus on the outside view of theproject, bringing with it wider rangesof potential durations for givenactivities.

Second, the dialogue that takesplace as part of the analysis processgreatly enhances the team’sknowledge of the project, schedule,and potential risks. Bringing as manyproject stakeholders as possibletogether to discuss all aspects of theproject tends to force each participantto look beyond their specific realm ofresponsibility. The result is that teammembers often change the durationsof their assigned work.

Another benefit of risk analysiscenters on risk identification. Baseplans rarely include delays or impactsresulting from risks inherent to theproject. Project schedules are oftendeveloped with the assumption thateverything will go as planned, thoughthis assumption is rarely supported.Equipment fabrications take longerthan quoted, underground

obstructions are discovered, weatheris worse than anticipated, productivityis not as good as estimated; the list ofcommon risks is endless. In addition,there are project-specific risks thatmay be even more impactful. If theteam can make an effort to identifythose risks and how they may affectthe schedule, its members willhighlight those risks that need to becarefully monitored and mitigated.

The probabilistic analysis resultsprovide valuable information to theproject team regarding alternatescenarios that can ultimately drive theproject’s schedule. Once the range ofdriving probabilistic critical paths isevaluated, the project can reserveschedule contingency in key locationsin the activity network to reflectpossible anticipated slippage in theplan [11]. The resulting “riskedschedule” becomes a more realisticplan when duration uncertainty isapplied to the project. Activemanagement of the risked projectschedule includes updating theanalysis periodically as executionchanges during the project’s life cycle.This approach can be an effectivesolution to overcoming the inherentbias present in early-date, critical pathmethod project schedules.

The Coach’s ChallengeSometimes the most useful thing

you can do for your project is to bringin an unbiased third party to facilitatea high-level planning session [1]. Thisis often practiced when performing aschedule risk analysis. Frequently,project teams are too close to thedetails and don’t want to accept analternate view of the project’sschedule risks. The concept of the“Coach’s Challenge” can be usedduring schedule review sessions. Thefacilitator or a designee has theauthority to throw a “challenge flag”when they see the team making adecision that does not make sensewhen looked at from an outside view.Like the Coach’s Challenge in theNational Football League, the flagthrow identifies a decision that needsto be more carefully looked at and


then tested for validity.Coach’s Challenges are most

frequently issued during the rangingsession of a schedule risk review.While working with team members todetermine optimistic and pessimisticdurations, it is not uncommon for thediscussion of an activity to highlight apotential risk or significant variance inthe planned duration from thatpreviously experienced. Theconsensus may be to extend theduration, but the person ultimatelyresponsible will disagree for any of thevarious reasons discussed previously.It is at this point that the challengeflag is thrown to focus the discussionon how the planned duration wasdeveloped. The discussion may eitherverify that the planned duration has asolid basis as currently shown, or maylead to a revision.

Less Collaborative Planning?The collaborative approach to

developing a project’s schedule isoften in contrast to how the project’scost is estimated. Even though thescope and associated quantities areoften reviewed with the full projectteam, the project’s estimate istypically developed independently.Estimated hours and cost arecomputed using detailed comparableand historical information as averifiable basis. Why are theseapproaches so different? Why doparticipants in a group scheduleplanning session feel so confident inproposing activity durations (oftenwith little or no basis), when theywould be very hesitant to throw outan estimate of its cost?

Research implies that planningfallacy effects are greater in a groupsetting than when task durations areestimated independently [3]. Whencombined with the often fragiledynamics that tend to surface duringgroup planning sessions, maybe thecollaborative planning techniqueshould not be the preferred approach.Perhaps project schedules should bedeveloped more like estimates: withextensive analyses of scope and other

factors that determine a project’scost, and in turn, its completion date.

In reality, the collaborativeplanning environment has too manyadvantages that offset its potentiallimitations. The commonunderstanding of the project scope,work breakdown structure, activities,and relationships is inherentlyvaluable to planning sessionparticipants. Key hand-off pointsduring execution of the work must beaccurately represented in theproject’s schedule. The personbuilding the schedule network is aprimary beneficiary of thesecollaborative planning sessions.

However, planning fallacylimitations of this group planningapproach suggest that more activityduration validation is needed beforeestablishing a schedule as the projectbaseline. External reviews,benchmarking, resource analysis, andhigh-level sanity checks are allvaluable techniques to combatpotentially optimistic and inherentlybiased project schedules. Whencombined with the synergisticbenefits of collaborative planning, thistwo-step approach can produce aschedule that is both accurate andbacked up with a solid basis for itsdurations.

SummaryThe planning fallacy is a tangible

influence that can lead to plannedschedules that are doomed to fail,even before a project starts.Optimistic and often biased estimatesof individual activity durations cancombine to produce a schedule thatseverely underestimates the totaltime needed to complete a project.The planning approach, especially in agroup environment, can oftenexacerbate the inside view taken by aproject team when proposing anoverly aggressive schedule.

Planning fallacy research showsthat other factors, such as memorybias, power influence, egos, groupoptimism, and level of detail, can playa major role during scheduledevelopment. An effective project

manager or planner will recognizethese effects and take steps tomitigate their impact on the schedule.Techniques like ordinal dates, a pre-mortem, the Coach’s Challenge, andrisk-adjusted schedules can often beused to offset unrealistically shortschedule durations. Effective projectteams welcome an outside view oftheir plan and use comparative datato validate and provide a solid basisfor their schedule.

An examination of the planningfallacy might suggest that the ultimatesolution is to simply extend plannedschedules out so that they reflect anoverly conservative estimate of theproject’s duration. In the projectworld, however, this approach issimply not viable. Projects should beplanned to complete in a sensibleamount of time, includingcontingency. Recognizing andovercoming potential planning fallacyissues during development willproduce better project schedules thatare both achievable and reasonable.

REFERENCES1. Birken, Emily Guy, 2014, This Is

Why Your Projects Always TakeLonger Than You Expect,WiseBread - Living Large on aSmall Budget (web site blog),June 16, 2014,www.wisebread.com.

2. Buehler, Roger; Dale Griffin, andMichael Ross, 1994, Exploring the"Planning Fallacy": Why PeopleUnderestimate Their TaskCompletion Times, Journal ofPersonality and SocialPsychology, Vol. 67, No. 3, Pages366-381.

3. Buehler, Roger; DeannaMesservey, and Dale Griffin,2005, Collaborative Planning andPrediction: Does Group DiscussionAffect Optimistic Biases in TimeEstimation?, OrganizationalBehavior and Human DecisionProcesses, Pages 47-63.

4. Flyvjberg, Bent, 2008, CurbingOptimism Bias and StrategicMisrepresentation in Planning:Reference Class Forecasting in



Practice, European PlanningStudies, Vol. 16, No. 1.

5. Gilovich, Thomas; Dale Griffin,and Daniel Kahneman, 2002,Chapter 14, Inside the PlanningFallacy: The Causes andConsequences of Optimistic TimePredictions, Hueristics and Biases- The Psychology of IntuitiveJudgment, Pages 250-270,Cambridge University Press.

6. Hadjichristidis, Constantinos;Barbara Summers, and KevinThomas, 2014, UnpackingEstimates of Task Duration: TheRole of Typicality and Temporality,Journal of Experimental SocialPsychology, Vol. 51, March 2014,Pages 45-50.

7. Kahneman, Daniel, 2011, Chapter23, The Outside View, Thinking,Fast and Slow, First Edition, Pages245-254, Farrar, Strauss andGiroux, New York.

8. Kahneman, Daniel; and AmosTversky, 1977, IntuitivePrediction: Biases and CorrectiveProcedures, Technical ReportPTR-1042-7746, DefenseAdvanced Research ProjectsAgency - Advanced DecisionTechnology, Decision Research,Eugene, OR.

9. Klein, Gary, 2007, Performing aProject Premortem, HarvardBusiness Review, September2007.

10. LeBoeuf, Robyn; and Eldar Shafir,2009, Anchoring on the “Here”and “Now” in Time and Distance

Judgments, Journal ofExperimental Psychology:Learning, Memory, andCognition, Vol. 35, No. 1, Pages81-92.

11. Ponce de Leon, Dr. Gui, 2013,Mitigating the Planning Fallacy(Risked Schedules - The NewNormal), 2013 NetPoint UserConference KeynotePresentation, PMA Technologies.

12. Roy, Michael; and NicholasChristenfeld, 2007, Bias inMemory Predicts Bias inEstimation of Future TaskDuration, Journal ofExperimental Psychology:Learning, Memory, andCognition, Vol. 35, No. 2, Pages557-564.

13. Roy, Michael; Scott Mitten, andNicholas Christenfeld, 2008,Correcting Memory ImprovesAccuracy of Predicted TaskDuration, Journal ofExperimental Psychology:Applied, Vol. 14, No. 3, Pages 266-275.

14. Vrable, Alina, 2013, PlanningFallacy: Why People Suck atPlanning, Sandglaz (web siteblog), November 15, 2013,http://blog.sandglaz.com/.

15. Weick, Mario; and Ana Guinote,2010, How Long Will It Take?Power Biases Time Prediction,Journal of Experimental SocialPsychology, Vol. 46, No. 4, Pages595-604.

ABOUT THE AUTHORS

Jeffrey Valdahl iswith PMAConsultants, LLC.He can becontacted bysending e-mail to:

[email protected]

Shannon A. Katt iswith PMAConsultants, LLC.She can becontacted bysending e-mail to:

[email protected]

FOR OTHER RESOURCESFor additional resources go to:www.aacei.org/resources/vl/

Do an “advanced search” by “au-thor name” for an abstract listing ofall other technical articles this authorhas published with AACE. Or, searchby any total cost management subjectarea and retrieve a listing of all avail-able AACE articles on your area of in-terest. AACE also offers pre-recordedwebinars, an Online Learning Centerand other educational resources.Check out all of the available AACE re-sources.

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