AACE Analisis de La Curva S

7/22/2019 AACE Analisis de La Curva S

1/20


2/20

Recommended Practice

Total CostManagement

Framework:

T&+a# C&*+Ma%age$e%+ * a*3*+e$a-c a'')&ach

+& $a%ag%g c&*++h)&/gh&/+ +he #fe

c3c#e &f a%3 e%+e)')*e7 ')&g)a$7 fac#+37 ')&!ec+7 ')&d/c+ &) *e)0ce:

AACE;* flag*h' '/b#ca-&%7 +he TCM F)a$e1&)"9 A% I%+eg)a+edA'')&ach +& P&),&7 P)&g)a$ a%d P)&!ec+ Ma%age$e%+7 * a*+)/c+/)ed7 a%%&+a+ed ')&ce** $a' +ha+ f&) +he fi)*+ -$e e2'#a%* each

')ac-ce a)ea &f +he c&*+ e%g%ee)%g fie#d % +he c&%+e2+ &f +*)e#a-&%*h' +& +he &+he) ')ac-ce a)ea* %c#/d%g a##ed ')&fe**&%*:

Visual TCMFramework:

V*/a# TCM g)a'hca##3de$&%*+)a+e* +he

%+eg)a-&% &f +he*+)a+egc a**e+

$a%age$e%+ a%d')&!ec+ c&%+)*')&ce** $a'* &f +he TCM F)a$e1&)": The V*/a# TCM a''#ca-&% ha*bee% de*g%ed +& ')&0de a d3%a$c 0e1 &f +he TCM ')&ce**e*7 f)&$+he &0e)a## *+)a+eg3 ')&ce** $a'* +& +he $d?#e0e# ')&ce**e* a%d

de+a#ed ac-0-e*: The ')&ce**e* a)e h3'e)#%"ed7 g0%g +he /*e) +heab#+3 +& $&0e +& a%d f)&$ )e#a+ed ')&ce** $a'* a%d )efe)e%ce


Th* Rec&$$e%ded P)ac-ce RP * b)&/gh+ +& 3&/ a*'/b#c *e)0ce b3 AACE I%+e)%a-&%a#7 +he A/+h&)+3 f&)T&+a# C&*+ Ma%age$e%+:

The AACE I%+e)%a-&%a# Rec&$$e%ded P)ac-ce* a)e+he $a% +ech%ca# f&/%da-&% &f &/) ed/ca-&%a# a%d

ce)-fica-&% ')&d/c+* a%d *e)0ce*: The RP* a)e a *e)e*&f d&c/$e%+* +ha+ c&%+a% 0a#/ab#e )efe)e%ce%f&)$a-&% +ha+ ha* bee% */b!ec+ +& a )g&)&/* )e0e1

')&ce** a%d )ec&$$e%ded f&) /*e b3 +he AACE

I%+e)%a-&%a# Tech%ca# B&a)d:

AACE I%+e)%a-&%a# * a Dc %&%?')&fi+')&fe**&%a# a**&ca-&% *e)0%g +he +&+a# c&*+$a%age$e%+ c&$$/%+3 *%ce KH: AACE

I%+e)%a-&%a# ')&0de* +* $e$be)* a%d *+a"ehde)*1+h +he )e*&/)ce* +he3 %eed +& e%ha%ce +he)'e)f&)$a%ce a%d e%*/)e c&%-%/ed g)&1+h a%d

*/cce**: W+h &0e) 7DD $e$be)* 1&)#d?1de7 AACEI%+e)%a-&%a# *e)0e* +&+a# c&*+ $a%age$e%+')&fe**&%a#* % a 0a)e+3 &f d*c'#%e* a%d ac)&** a##

%d/*+)e*: AACE I%+e)%a-&%a# ha* $e$be)* % c&/%+)e*: If 3&/ *ha)e &/) $**&% +&


3/20

$a%age$e%+: C&$')ehe%*0e7 1e## &)ga%4ed7 a%d -$e#37 each PPG * a

c#ec-&% &f *e#ec+ed a)-c#e* c&0e)%g a 'a)-c/#a) +ech%ca# +&'c a)ea&) %d/*+)3 *eg$e%+: The PPG* ')&0de a% e2ce##e%+ *&/)ce &f )efe)e%ce$a+e)a# a%d * a 1e#c&$e add-&% +& a%3 )efe)e%ce #b)a)3:

Certification:

S%ce KH7 AACE ha*

bee% ce)-f3%g%d0d/a#* a* Ce)-fiedC&*+ C&%*/#+a%+*CCC>Ce)-fied C&*+

E%g%ee)* CCE8Ce)-fied C&*+Tech%ca%* CCT8

Ce)-fied E*-$a-%g P)&fe**&%a#* CEP8 Ce)-fied F&)e%*c C#a$*C&%*/#+a%+* CFCC8 Ea)%ed Va#/e P)&fe**&%a#* EVP8 a%d P#a%%%g Sched/#%g P)&fe**&%a#* PSP: I% +he $d*+ &f *+agge)%g b/*%e** a%d

ec&%&$c +/)$ 3&/ %eed a## +he +&* a+ 3&/) d*'&*a# +& he#' *h&)e/' 3&/) ca)ee) ')&*'ec+*: AACE ce)-fica-&% ca% he#' 3&/ a%d +he&)ga%4a-&%* +ha+ )e#3 &% 3&/ f&) he#'5

Online Learning

Center:

The O%#%e Lea)%%gCe%+e) fea+/)e*$&d/#e* ba*ed /'&%ac+/a# +ech%ca#

')e*e%+a-&%* ca'+/)ed

$a+e)a#: Th* a##&1* f&) +he &'-$a# effec-0e%e** &f /%de)*+a%d%g a%d

/*%g +he ')&ce** a%d */b?')&ce** % +he c&%+e2+ &f a%d )e#a-&%*h' +&a**&ca+ed */b?')&ce**e* +ha+ *ha)e c&$$&% *+)a+ege* a%d &b!ec-0e*:V*/a# TCM a##&1* +he /*e) +& 0e1 a%d a''#3 TCM *ec-&%?b3?*ec-&%7

a+ a */b?')&ce** &) f/%c-&%a# #e0e#: V*/a# TCM * a0a#ab#e +& $e$be)*a+ %& e2+)a fee:

Virtual Library:

Me$be)* )ece0e f)eeacce** +& +he V)+/a#Lb)a)37 a% &%#%e

c#ec-&% &f &0e) DDDc&$'#e+e +ech%ca#a)-c#e* &% 0)+/a##3

e0e)3 a*'ec+ &f c&*+e%g%ee)%g: Sea)ch+h* e2+e%*0e da+aba*e a%d $$eda+e#3 )e+)e0e +he be*+ +ech%(/e*

a%d '&+e%-a# */-&%* +& +he ')&b#e$* c&%f)&%-%g 3&/ a%d 3&/)&)ga%4a-&%:

ProfessionalPractice Guides(PPGs):

P)&fe**&%a# P)ac-ceG/de* c&%+a% +he

$&*+ 1&)+h1h#ec&%+)b/-&%* +& +hefie#d &f +&+a# c&*+

Recommended Practice Recommended Practice
http://www.aacei.org/educ/cert/http://www.aacei.org/resources/vl/http://www.aacei.org/resources/ppg/https://live.blueskybroadcast.com/bsb/client/CL_DEFAULT.asp?Client=502522http://www.aacei.org/mbr/how2join.shtmlhttp://www.aacei.org/mbr/how2join.shtml


4/20

DiscussionForums:

The d*c/**&% f&)/$*

e%c&/)age +hee2cha%ge &f +h&/gh+*a%d dea*7 +h)&/gh'&*-%g (/e*-&%* a%d

d*c/**%g +&'c*: The3')&0de a g)ea+ $ea%* f&) %e+1&)"%g a%d %+e)ac-&% 1+h 3&/) 'ee)*:

Pa)-c'a+e a%3-$e a+ 3&/) c&%0e%e%ce a%d )ece0e a/+&$a-c e?$a#%&-fica-&%* &% +&'c* +ha+ a)e &f %+e)e*+ +& 3&/: W+h *e0e)a# +h&/*a%d/*e)*7 f 3&/ ha0e (/e*-&%* &) c&%ce)%* ab&/+ a +ech%ca# */b!ec+7')&g)a$7 &) ')&!ec+ ? +he f&)/$* a)e a g)ea+ )e*&/)ce f&) 3&/:

MentoringProgram:

L&&"%g +& ga% $&)e

"%&1#edge f)&$ a%e2'e)e%ced')&fe**&%a# &) a%

&''&)+/%+3 +& he#'

a%&+he) ')&fe**&%a#6I%c#/ded 1+h 3&/) $e$be)*h'7 AACE &ffe)* a c&$')ehe%*0e

$e%+&)%g ')&g)a$ f&) %d0d/a#* %+e)e*+ed % *ha)%g "%&1#edge 1+h&+he)* &) ad0a%c%g +he) &1% ca)ee)* +& +he %e2+ #e0e#:


a+ &/) A%%/a# Mee-%g*: Each )ec&)ded /%+ %c#/de* a #0e a/d&

)ec&)d%g &f +he *'ea"e) *3%ch)&%4ed +& +he *#de* acc&$'a%3%g +he')e*e%+a-&%: Each /%+ %c#/de* +he +ech%ca# 'a'e) a**&ca+ed 1+h +he')e*e%+a-&%7 a%d a d&1%#&adab#e a/d&?&%#3 0e)*&% +ha+ 3&/ $a3 '#a3

&% 3&/) $&b#e de0ce &) P&d: C&$'#e-&% &f each /%+ ea)%* D: AACE)ece)-fica-&% c)ed+* :e: D: CEU*: A% e#ec+)&%c ce)-fica+e &fc&$'#e-&% 1## be a.ached +& 3&/) ')&fi#e:

Conferences:

AACE I%+e)%a-&%a#;*A%%/a# Mee-%g b)%g*

+&ge+he) +he %d/*+)3;*#ead%g c&*+')&fe**&%a#* % a

f&)/$ f&c/*ed &%#ea)%%g7 *ha)%g7 a%d%e+1&)"%g: O0e) DD

h&/)* &f +ech%ca# ')e*e%+a-&%* a%d a% %d/*+)3 +)ade*h&1 +ha+ 1##cha##e%ge 3&/ +& be.e) $a%age7 '#a%7 *ched/#e7 a%d $'#e$e%++ech%&g3 f&) $&)e effec-0e a%d effice%+ b/*%e** ')ac-ce*:

The I%+e)%a-&%a# TCM C&%fe)e%ce * a *$#a) e0e%+ +ha+ * he#d &/+*de&f N&)+h A$e)ca @ c&$'#e+e 1+h +ech%ca# ')e*e%+a-&%*7 *e$%a)*

a%d e2hb+*:

http://www.aacei.org/resources/lc/http://www.aacei.org/am/currentAM/http://www.aacei.org/career/mentor/http://www.aacei.org/mbr/how2join.shtmlhttp://www.aacei.org/mbr/how2join.shtml


5/20

Periodicals

Me$be)* )ece0e ac&$'#$e%+a)3*/b*c)'-&% +& +he

C&*+ E%g%ee)%g!&/)%a#7 AACE;*b?$&%+h#3

')&fe**&%a##3'ee)?)e0e1ed '/b#ca-&%: I+ c&%+a%* be*+?%?c#a** +ech%ca# a)-c#e* &%

+&+a# c&*+ $a%age$e%+ )e#a+ed */b!ec+*:I+ * '/b#*hed a* b&+h a ')%+ 0e)*&% a%d a% &%#%e 0e)*&%:

O/) b?$&%+h#3 dg+a# '/b#ca-&%7 S&/)ce7 f&c/*e* &% AACE ac-0-e*a%d +e$* &f %+e)e*+ +& +he +&+a# c&*+ $a%age$e%+ c&$$/%+37 1+h

*'eca# fea+/)e* f&) &/) $e$be)*:


Career Center:

AACE;* ca)ee) ce%+e)')&0de* +&* a%d)e*&/)ce* f&) 3&/ +&

')&g)e** +h)&/gh 3&/)ca)ee):

L&&"%g f&) +he %e2+)/%g &% +he ca)ee) #adde) &) +& h)e +he +a#e%+ %ece**a)3 +& +a"e 3&/)

fi)$ +& +he %e2+ #e0e#6 J&b *ee"e)*7 /*e &/) *e)0ce* +& fi%d 3&/) %e2+!&b @ '&*+ 3&/) )e*/$e7 ge+ e?$a# %&-fica-&%* &f %e1 !&b?'&*-%g*7a%d $&)e: E$'#&3e)*7 '&*+ 3&/) c/))e%+ !&b?&'e%%g* a%d *ea)ch &/)e2+e%*0e )e*/$e da+aba*e +& fi%d 3&/) %e2+ *+a) e$'#&3ee:

Salary andDemographicSurvey:

C&%d/c+ed a%%/a##37*a#a)3 */)0e3 * a g)ea+)e*&/)ce f&)

e$'#&3e)* +ha+ 1a%+

+& ga% a be.e)/%de)*+a%d%g &f +he c&$'e--0e $a)"e+'#ace f&) +a#e%+ a%d f&)

e$'#&3ee* %+e)e*+ed % "%&1%g h&1 +he) c&$'e%*a-&% c&$'a)e*1+h +he) 'ee)* % +he ')&fe**&%:

http://www.aacei.org/career/http://www.aacei.org/resources/magazines.shtmlhttp://www.aacei.org/resources/salary/http://www.aacei.org/mbr/how2join.shtmlhttp://www.aacei.org/mbr/how2join.shtml


6/20

Copyright 2010 AACE International, Inc. AACE International Recommended Practices

AACE International Recommended Practice No. 55R-09

ANALYZING S-CURVESTCM Framework: 10.1 Project Performance Assessment

Acknowledgments:Jeff Goodman, PSP (Author)Timothy T. Calvey, PE PSPChristopher W. Carson, PSP

Andrew DickAnthony L. JervisDennis R. Hanks, PE CCEDonald F. McDonald, Jr. PE CCE PSPVicente A. Ruiz

Donald E. Parker, PE CCEHannah E. Schumacher, PSPWilliam James Simons, PSPJerry L. Vogt, PSPRonald M. Winter PSPDavid C. WolfsonJames G. Zack, Jr., CFCC


7/20


AACE International Recommended Practice No. 55R-09

ANALYZING S-CURVESTCM Framework: 10.1 Project Performance Assessment

November 10, 2010

PURPOSE

This recommended practice (RP) for analyzing S-curves is intended to serve as a guideline, not toestablish a standard. As a recommended practice of AACE International, analyzing S-curves providesguidelines for stakeholders of a project to evaluate the current status and trends of a project in a simplegraphical format.

S-curves are usually developed by a project scheduler or cost engineer and can be applied on a variety ofproject types. The product is generally used as a project management and/or total cost management(TCM) tool for graphic representation of project performance.

The RP provides descriptions of S-curves with the intent to improve understanding and communicationamong project participants and stakeholders when preparing and analyzing graphics based upon projectschedule information. The RP describes different types of S-curves that may be generated from a

schedule provided the proper information is loaded into the schedule and the status of the information ismaintained throughout the duration of the project.

OVERVIEW

An S-curve is a graphic display of cumulative costs, labor hours, progress, or other quantities plottedagainst time. The term derives from S-like shape of the curve, flatter at the beginning and end andsteeper in the middle, which is typical of most complex projects. Most projects start slowly, acceleratethroughout the majority of the work and then slow down again near the end as productivity declines andwork runs out.

The term S-curve can also be used to indicate an S shaped chart resulting from a cumulative likelihooddistribution. In this function, an S-curve is a tool of quantitative risk analysis which project managementwould use to determine the possible dangers of any given course of action.

S-curves are also called, cumulative distribution charts, velocity diagrams, and SPLOTS (S-plots.)

RECOMMENDED PRACTICE

AACE recommends that schedulers and other project team members develop and use S-curves to plan,monitor, analyze, forecast and control project progress. Project managers should request that projectcontrols personnel produce and use this graphical technique as a tool for briefing stakeholders on projectstatus and trends in a quick and intuitive manner.

DEVELOPING S-CURVES

Prior to developing an S-curve, a project baseline schedule needs to be developed. The baselineschedule should employ best scheduling practices (i.e. documentation of scheduling basis, start, finish,no open ends, minimal constraints, a defined critical path, etc.). The baseline schedule should alsocontain cost and/or quantity data information if that type of S-curve is desired. The S-curve produced fromthe baseline early dates is often referred to as the target S-curve which reflects projected or plannedprogress on the project if all tasks are completed on their original early finish dates. This curve representsthe best progress or productivity that can be expected. It is important that the cost and/or quantityinformation loaded into the activities represents the appropriate time-scaled values for those activities.


8/20


Analyzing S-Curves

November 10, 2010

2 of 14

For example, if electrical service equipment will be delivered in one large shipment and then installedover a three month time period, the large cost of the equipment will be earned when delivered, so thatcost should be loaded into the delivery activity, and the balance of the costs can be loaded into theinstallation activity. When loading costs into activities, the activities should reflect a straight-lineconsumption of those costs (a ten day activity with a $10,000 cost should reflect installation of $1,000 per

day). This methodology of loading costs into the schedule will result in reasonable and appropriate S-curves.

S-curves were generated traditionally within the C/SCSC (Cost/Schedule Controls Systems Criteria)process that evolved into the present Earned Value Management System.

1. Common S-Curves:

A variety of S-curves exist, the most common being man hours versus time, and costs versus time. Whilethe S-curves generated using any quantities versus time that are useful for comparison, such as volumeof concrete or linear footage of pipe, the S-curves generated using cost versus time may be helpful indeveloping the projects overall cash flow. The time unit used is typically monthly to coincide with normal

monthly project status updates. Weekly and even daily time units are also used. The smaller the time unitbetween readings, the smoother the S-curve will be and easier to use for forecasting trends.

The shape of the S-curve may yield significant information about the nature of the project. Curves thatstart up steeply and then flatten out may indicate front-loading, which could be projects that require littleor no planning time, repair of disaster damage, or they could indicate a schedule that has beenaccelerated from the beginning. Curves that start out with a lower slope and then run steeply tocompletion could indicate a large planning or design time in the beginning and a reduced constructiontime.

If the project is primarily labor, generally those curves are typically back-loaded, initially flat andincreasingly steep towards the end of the project. Projects where the costs are mostly installed materialsand labor tend to show a fairly linear distribution of costs over time. Mobilization costs and deposits willcause more front-loading of the curve.

1.1. Progress S-Curves:

After creating a baseline schedule, a baseline S-curve should be generated. Baseline S-curves providethe basis on which to compare a project's actual status to its planned progress. There are two types ofcomparisons that can be developed (for simplicitys sake Figure 1 and 2 below reference hours but, justas easily could be replaced with costs):

Figure 1 Target Plan Man Hours vs. Actual Man Hours Expenditure


9/20


Analyzing S-Curves

November 10, 2010

3 of 14

Figure 2 Target Plan Man Hours vs. Earned Man Hours (Based on Plan)

The two comparisons can be combined with a target or earned vs. actual comparison which can provideinsight as to manpower and financial resources required to complete the project.

Schedules with status applied to them are called updated schedules. One can produce the same type ofS-curves as produced with the baseline schedule to track actual progress and to forecast upcomingprogress. S-curves produced from update schedules are typically similar but different than thoseproduced from the baseline schedule in that they also display curves derived from earned and actualdata.

The baseline schedule provides target progress, typically in costs or man hours. The update schedulemay provide three basic metrics; the value of the work that was planned to be achieved at the time of theupdate, the actual value of the work achieved at the time of the update and the earned progress typicallyshows earned costs or earned man hours at the time of the update. Payrolls or other man hour reportsprovide actual man hours expenditures.

Updated project schedules and payrolls/timecards provide the actual data that is then compared to thebaseline S-curves. This allows the progress of a project to be monitored and quickly reveals anydivergence from the baseline schedule. S-curves may also be used to depict project growth, slippage,and progress.

The two values that are generated in updated schedules are different in that the earned value is derivedfrom the accumulation of the percent complete of the individual activities times their planned quantities orcosts, and the actual value is derived from either manual entry of actual job costs or the calculations ofthe completed activities values along with the calculation based on the estimates of remaining durationsof those activities. Obviously, if the project management team can provide actual job values or quantitiesto be entered into the system, the actual curves will be accurate and valuable. Without actual real-time

job data, the software used generally defaults to its own algorithms for the calculations of completion in

the schedule. If the remaining duration and the percent complete components of the schedule are linkedsuch that one calculates from the other, then the two available curves will be identical and offer noseparate analysis ability. For this reason, it is important that the schedule software is set to calculatepercent complete and remaining duration separately, allowing time and values to be represented in thecurves. When discussing cost loaded schedules, the actual costs curves are generated from percentcomplete of activities (hopefully based on quantities or costs) and the earned value curves are generatedfrom remaining duration calculations based on time.


10/20


Analyzing S-Curves

November 10, 2010

4 of 14

1.2. S-Curves with Early and Late Dates:

Most scheduling software can provide the information that calculates the cost, hours, and/or quantity datain the schedule over the both the early dates (forward pass of the schedule) and the late dates (backwardpass of the schedule). These are sometimes referred to as banana curves. The two curves will typically

only overlap at the beginning and end of the project. The envelope produced by these two curvesrepresents the range of possibilities that the project can expect if it is to be delivered on time. It isimportant to note that the lower range of the banana curve, the late date curve, is the prediction ofprogress where every single activity is performed on the last available day and all work is on the criticalpath. This means that if any single activity on the late date curve slips, the project slips. Stakeholdersshould be concerned about performance risk when a project planned or actual curve is tracking close tothe late date curve.

This information can then easily be put in a graphical format as shown in figure 3 below:

Figure 3 Typical S-Curve with Early and Late Dates

1.3. Quantity S-Curve:

Another common useful type of S-curve found in the manufacturing and construction industries is the

quantity S-curve. It uses the production schedule and graphs the quantity versus schedule time. Here thequantity information loaded into the baseline schedule which is tracked along with actual quantities. Thisallows the progress of a project to be monitored, and quickly reveal any divergence from the baselineschedule. These production S-curves may also be used to depict project growth, slippage, and progressto date. For comparative purposes one could plot planned versus actual quantities.


11/20


Analyzing S-Curves

November 10, 2010

5 of 14

Figure 4 Quantity Output S-Curve

1.4. Cash Flow S-Curves:

Cash flow is the movement and timing of cash with respect to the events in a project. Depending on theultimate purpose, constructing the cash flow curve has various requirements. The stakeholders of theproject have various interests in the curve. One primary use of developing the cash flow curve is to seeneed for cash, and the timing of the payment obligations. It is significant to clearly understand that withoutgood financial health there would not be a project.

On a fixed price contract, stakeholders are concerned with the most complex timing considerations; the

work actually performed or earned as well as related expenditures and revenue payments. Each of thesemay have multiple timing considerations. Other contract types have some, but not all of theseconsiderations.

Thus, in order to produce a realistic useful cash flow curve must consider the timing of each cost element.If the estimate classified cost by cost type (labor, material, equipment, subcontracts, etc.] and the cost isloaded into schedule as resources in the same categories, then the early/late curves can be graphed bycost type. Obviously, the S-curve on which all these calculations are based should be the optimalresource-based curve, on the median of the early and late curves.

1.5. Other Specific S-Curves:

Depending on the data and information loaded into schedule activities there are numerous types of S-curves the can be developed. The following is a brief list of common types of S-curves:

Resources Manpower Installed quantities WBS


12/20


Analyzing S-Curves

November 10, 2010

6 of 14

PROGRESSING S-CURVES

Once the baseline S-curve is graphed and actual progress status information is obtained for the project,the actual progress can be graphed along with the baseline or target S-curve.

The progress S-curve with the baseline/target S-curve provides stakeholders with information onvariances and trends. Earned value and performance information may also be generated and displayedon the common S-curve graph. The variances in cost/quantity and schedule can readily be seen and byanalyzing the results relative to the baseline/target S-curve, forecasts can be made of anticipatedvariations at completion.

S- CURVE ANALYSIS

S-curves based upon actual data can be used to monitor the project as it progresses and comparison ofactual progress to the projected S-curve helps to determine whether the project will be completed withinthe time and budget limitations. There are several methods of analyzing the S-curve.

The methods will be discussed in this RP are applying actual data, applying earned value, applyingearned schedule and applying common shapes of early and late dates to the S-curve. The analysismethod used may depend on the complexity of the project and contractual requirements.

1. S-Curve Analysis Applying Actual data:

The easiest S-curve analysis method to use is applying actual data to the S-curve. This provides aneasily understood view of project status. Below are two examples of actual data applied to S-curves alongwith a brief analysis for the curve.

Figure 5 Quantity Output S-Curve


13/20


Analyzing S-Curves

November 10, 2010

7 of 14

The above S-Curve suggests that since the actual data is below the planned value the project is behindschedule. Any given actual quantity figure is only reached later than it was planned to be. Conversely, ifthe actual data line was above the planned line, the graphic would indicate the project is currently trackingahead of schedule.

Figure 6 Early/Late Date S-Curve with Actual Progress

In the above example, the actual data is plotted along with the early and late date information from theschedule. The analysis of this graph indicates that as long as the actual data falls between the early andlate dates and the forecasted completion is on or before the end date, the project is in good standing.

This plot does not guarantee project success; it only indicates that the actual work appears to be withinplanned boundaries. Again, note that the closer that actual data conforms to the late dates, the higher therisk of project delay, especially with resource limitations compared to the resource logic used in theschedule. A project that is tracking along the late dates in the first 85% of the project has a high likelihoodof slipping past the predicted completion and should be analyzed carefully for the resource requirementsto complete the project.

2. S-CurveAnalysis Earned Value:

Another common method of analysis of the S-curve for a project is with earned value. Earned valuemanagement is a method of integrating scope, schedule, and resources into a discrete set of numbersand then objectively measuring the project performance and progress using these values. Below are two

examples of applying actual and earned data to S-curves along with a brief analysis of the curve.


14/20


Analyzing S-Curves

November 10, 2010

8 of 14

Figure 7 Earned Value S-Curve

In figure 7 above, the planned line is the performance baseline from the schedule and is considered thebenchmark S-curve against which actual performance is analyzed. The figure above shows the projectcurrently anticipates an early finish but with additional costs or quantities from the performance baseline.This information should be evaluated with the project stakeholders to determine if this is the best coursefor the project.

Figure 8 depicts a hypothetical situation where a known problem and its projected impact are being

considered.


15/20


Analyzing S-Curves

November 10, 2010

9 of 14

Figure 8 Earned Value S-Curve

In the above graph, the planned line is the performance baseline from the schedule and is consideredthe primary S-curve being analyzed. The graph above shows the project currently anticipates a cost orquantity overrun, together with possible corrective action(s) as well as finishing beyond the originalplanned finish date. The reason for the delay and forecast overrun should be brought to the projectstakeholders to determine the best course of action for the project. In order for the project to regain lost

time in order to complete on time, it will be necessary for the performance to be strong enough to allowthe S-curve to change slope enough to meet the completion milestone. This can be plotted and used todetermine progress necessary to complete on time, or the S-curve for recovery schedules that areproduced can be reviewed to see that the curves are sufficient.

It is also possible to separate out individual trades to graph earned value curves and that can be veryuseful in analyzing the performance of those trades as well as predicting the impact of the tradesperformance on the project.


16/20


Analyzing S-Curves

November 10, 2010

10 of 14

Figure 9 Earned Value S-Curve basic analysis

Figure 9 identifies from a graphical view some of the types of analysis that can be performed usingearned value. For the purpose of this RP, earned value terms will be introduced and a high level ofvariance analysis will be identified.

The axis are defined as X=Time and Y=Cost/Quantity

Budgeted Cost of Work Scheduled (BCWS)/Planned Value (PV) The sum of all budgets for workscheduled to be accomplished within a given time period.

Budget at Completion (BAC) The total authorised budget for accomplishing the project scope.

Actual Cost of Work Performed (ACWP)/Actual Cost (AC) The costs actually incurred inaccomplishing the work performed.

Budgeted Cost of Work Performed (BCWP)/Earned Value (EV) The value of the completed workexpressed in terms of the budget assigned to that work.

Estimate to Complete (ETC) The expected remaining cost needed to complete an activity, groupof activities or the project.

Estimate at Completion (EAC) The expected total cost of an activity, group of activities or theproject. Generally AC+ETC

Schedule Variance (SV) The time difference between the planned and earned schedule -expressed as a time variance (days, weeks, months, years). SV indicates how much ahead or behindthe project schedule is compared to the planned (Baseline). Generally a positive value indicates afavourable position and a negative value indicates an unfavourable position.

Cost Variance (CV) The difference between the EV and the PV expressed in dollars, generally apositive value indicates a favourable position and a negative value indicates an unfavourable position


17/20


Analyzing S-Curves

November 10, 2010

11 of 14

Variance at Completion (VAC) The difference between the BAC and the EAC. A positive valueindicates a favourable position and a negative value indicates an unfavourable position.

The BCWS (PV), BCWP (EV), and ACWP (AC) are graphically presented on an S-curve to identify

variances and present the status of a project.

3. S-CurveAnalysis Earned Schedule:

The concept of earned schedule is one where earned value is converted to progress in time along theprojected baseline progress curve. This computation indicates what the date should be if earned progresswere proceeding exactly according to plan. The comparison of the earned progress date and the statusdate will reveal how many days the project is behind or ahead.

Figure 10 Earned Schedule S-Curve

The planned line is the performance baseline from the schedule and is considered the benchmark S-curve against which actual performance is analyzed. The time variance between the planned andearned determines the forecasted completion date for the project.

6. S-CurveAnalysis Early and Late Dates:

There are many shapes that banana curves may take depending on the project. Three examples areprovided below. While any of these shapes may be acceptable depending on the project, the use ofhistorical S-curves from similar projects will help validate the S-curve shape.


18/20


Analyzing S-Curves

November 10, 2010

12 of 14

Figure 11 Example A

The banana S-curve shown above in Example A may indicate that there are excessive float values on theactivities at the end of the project schedule. This could result from the logic ties particularly at the endproject and these activities may require some analysis. The early date target line reaches completion wellbefore the late finish date target line. This banana curve may indicate that the project scope is notrequired to finish anywhere near this early. So one may look at the underlying logic and ask the question,Can this work be allowed to occur this soon as the result of the early completion of this scope? Thisbanana S-curve may be fine for the particular project or it may indicate something about the underlyingschedule logic of the project.

Figure 12 Example B


19/20


Analyzing S-Curves

November 10, 2010

13 of 14

The banana S-curve shown above in Example B is another indicator of potential problems, usuallycaused by excessive float due too relationship ties of logically staggered activates are linked into acommon successor. The effect is a nice looking early target curve but a bloated looking late target curve.

An obvious legitimate reason for this is when you have a detailed engineering schedule but theconstruction schedule is not yet fully developed. Also, there are two key points of analysis from the

banana S-curve in Example B that may need further examination. First, there is potentially someexcessive float in the schedule that goes against best practices which may contribute to the shape of theS-curve, but more importantly, this indicates that the late activities may not be resource leveled. Thisresults in schedule activities sliding to the far right as possible (as shown in the late curve above). Theproject will then have too much work stacked up at one time at the end of the schedule and may becomeimpossible from a resource perspective to complete. These types of banana curves at the projectsummary level may indicate that the schedule is not yet logically complete.

Figure 13 Example C

The banana S-curve in Example C tells us that the schedule is very tight (little activity float). This may notbe reasonable unless it is being caused by excessive use of contingency, or a limited number of parallelactivities.

There are two potential methods to further analyze S-curves. First, is to consider internal rules of thumbfor what percentage of activities in a schedule should have varying degrees of criticality (this will vary fromindustry to industry and project to project). The second is to review historical curves to see how closesimilar projects S-curves compare.

7. S-Curve Analysis Cautions:

It is possible for S-curve information to be misleading instead of instructive. For example, if the project istracking costs and has pre-ordered several high-ticket items, then the cost S-curve may show excellentprogress regardless of the current status of the critical work. In another example, poor productivity willalso show a high cost S-curve while schedule progress will be lower than expected.

Progress S-curves indicate cumulative progress of all work, not just critical work. The project may be


20/20

Analyzing S-Curves

November 10, 2010

14 of 14

behind due to over-emphasis on non-critical work at the expense of the critical work and still showexcellent S-curve progress.

The S-curve by itself and without any other project information (project status narrative, detail scheduleanalysis, etc.) may provide a false view of the project. Used in conjunction with other sound project

controls practices, S-curves can provide project stakeholders quick and meaningful indications of theoverall progress of the project.

SUMMARY

There are several different methods to generate and analyze an S-curve for a project. The complexity ofthe project, the project contract structure and value of the project are just a few factors in determining thebest type of S-curve that can be utilized on a particular project. The S-curve together with a CPMschedule is a tool that may be used by the stakeholders to status, evaluate and forecast the project.

REFERENCES

1. Hollmann, John K., PE CCE, Editor, Total Cost Management Framework: An Integrated Approach toPortfolio, Program and Project Management, AACE International, Morgantown, WV, 2006.

2. AACE International Recommended Practice 10S-90, Cost Engineering Terminology, AACEInternational, Morgantown, WV, (latest revision).

3. Project Management Institute, A Guide to the Project Management Body of Knowledge (PMBOKGuide), 4thEdition, Project Management Institute, Newtown Square, PA, 2008

4. Kerzner, Harold, Project Management: A Systems Approach to Planning, Scheduling, andControlling, 10th Edition, Wiley, Hoboken, NJ, 2009

5. OBrien, James J., Plotnick, Fredric L., CPM in Construction Management, 6thEdition, McGraw-Hill,New York, NY, 2006

6. Hutchings, Jonathan F., CPM Construction Schedulers Manual, McGraw-Hill, New York, NY, 19967. Lipke, Walter H. and Kym Henderson, Earned Schedule: An Emerging Enhancement to Earned Value

Management, CrossTalk - The Journal of Defense Software Engineering, Hill AFB, UT, November

20068. Midori Media, The Mysterious S Curve, PROJECTmagazine, 20039. AACE International Recommended Practice 38R-06, Documenting the Schedule Basis, AACE

International, Morgantown, WV, (latest revision).

CONTRIBUTORS

Jeff Goodman, PSP (Author)Timothy T. Calvey, PE PSPChristopher W. Carson, PSP

Andrew DickAnthony L. Jervis

Dennis R. Hanks, PE CCEDonald F. McDonald, Jr. PE CCE PSPVicente A. RuizDonald E. Parker, PE CCEHannah E. Schumacher, PSPWilliam James Simons, PSPJerry L. Vogt, PSPRonald M. Winter PSPDavid C. WolfsonJames G. Zack, Jr., CFCC

Documents

AACE Analisis de La Curva S