Systems Engineering Schedule/Effort Relationship Estimation, the
SCHEDESTSE COSYSMOR Tool Function
The principal output of the COSYSMOR tool is an estimate of the systems engineering
effort, K, corresponding to a value of Equivalent Requirements (EReq), S, the size of the
systems engineering job. Typically, the person who develops the estimate will also be
interested in the amount of time, or schedule, T, required to perform the systems
engineering job. The SCHEDESTSE COSYSMOR tool function enables the estimator to
determine the value of T, schedule or amount of time corresponding to the value of K
estimated by COSYSMOR for a given value of S. Thus, the estimator first employs
COSYSMOR to estimates K effort and then he uses the SCHEDESTSE COSYSMOR
tool function to estimate T, schedule (assuming that he is interested in a value for that
project parameter).
Often, the schedule for performing the systems engineering work on project will be
imposed upon those who will perform the systems engineering tasks. However, it may
also be of interest and value to the person performing the estimate as well as the proposal,
program or technical managers whom he is supporting to learn what schedule or effort
duration would be expected to correspond to the effort estimate produced by
COSYSMOR. This value of schedule may be smaller than, greater than, or equal to the
schedule value that might be imposed upon those performing the systems engineering
tasks.
An issue of considerable importance to proposal managers, program managers, technical
planners and to software engineering and systems engineering managers is how schedule
compression or stretch-out affects engineering costs or overall project costs. Schedule
compression (or stretch-out) can be defined as the amount or percentage of reduction
(increase) of a project or software or systems engineering schedule with respect to some
ideal or nominal value as related to cost or productivity. For COSYSMOR, the ideal or
nominal schedule value is taken to be a value based on past project experience, for the
relevant domain, captured and used as part of the tool calibration process. The calibration
process for schedule estimation purposes is described below and on the
SCHEDESTSECALIB tool page. It employs at least three sets of values, <S,K,T> from
actual systems engineering jobs to produce two functions, one of the form T=g(K,S) and
the other of the form S=fn(K,T). The former takes T to be the dependent variable and K
and S to be the independent variables. The latter takes S to be the dependent variable and
K and T to be the independent variables; it is of the form of a Cobb-Douglas Production
(CPD) function used in various economics analyses. The CPD function assumes that the
“factors of production,” K (labor) and T (time) are applied to produce a certain amount of
product of size or amount, S. The two functions, g and fn, are obtained by regression.
Which variables are taken to be dependent and which are taken to be independent
corresponds to the questions asked about the sets of data <S,K,T>. Also, note that the
COSYSMOR calibration process also uses a function, K=h(S)=A*SE, where A and E are
obtained using regression not further discussed to calibrate COSYSMOR for application
in its function of estimating K, systems engineering effort. The values of the parameters
1
of these functions are developed as part of the COSYSMOR calibration process, based on
actual systems engineering experience. It is preferred that the data used for calibration be
from projects that are similar to (in the same domain as) the project being estimated using
COSYSMOR.
The SCHEDESTSE COSYSMOR tool function enables the systems engineering
estimator to obtain the answers to two principal questions:
1. What is the value of T, call it T1 the nominal or natural value of the schedule,
that corresponds to the value of K, effort, call it K1, that the estimator obtained
using COSYSMOR? As described below, the empirical function T=fn(K,S),
implemented in the SCHEDESTSEUSER tool page, is used to answer that
question.
a. A subsidiary question is: Does the estimator accept this value of T, T1?
That is, Does it meet project criteria, or is it too large (long) or too
small (short)? Suppose that the answer is that the estimator does not
accept this value, but rather wants a different value of T, call it T2, say
that is imposed by the program manager. Then, the estimator proceeds
to question 2.
2. What is the value of K, call it K2 ,that corresponds to the desired value of
schedule,T2 ,e.g., one imposed upon the systems engineering job by the
proposal manager or by the program manager ? As described below, the
empirical function S=fn(K,T), was the basis for the implementation in the
SCHEDESTSEUSER tool page that is used to answer that question. This
implementing function is K2=func(T1,T2,K1); the derivation is described on
the SCHEDESTSECALIB tool page.
In typical usage, the person doing the systems engineering estimate would first employ
COSYSMOR to estimate systems engineering labor hours as described elsewhere in this
User Manual. Be mindful of the fact that COSYSMOR estimates a range of effort
estimate values. So, you would have to pick one, say the one that you chose to be THE
project labor estimate that you take to the customer. This might be one at a stated value of
risk, say 50%, as determined by COSYSMOR. What EReq (Equivalent Requirements)
value do you employ? You might select the one that you take to the customer. You
should consider the value of Unit Effort, Person Hours/EReq, resultant from your choice
of person hours and Equivalent Requirements, to ensure that this value of Unit Effort
“makes sense,” i.e., is in the range experienced in the projects used to calibrate
COSYSMOR.
The
Schedule/Effort
Relationship
Estimator
tool,
the
SCHEDESTSEUSER COSYSMOR tool page, calculates this value for you. Your next
step is to decide whether you wish to use that value of schedule. Is it too long or too
short? If you are satisfied with that value, then you are done. However, if you are not
satisfied with that value, but want another value,T2, then you use the
SCHEDESTSEUSER COSYSMOR tool page to estimate the value of effort, K2, that
corresponds to the desired value of schedule, T2.
2
A principal result of the schedule estimation process described above is the value of
schedule that you have selected, T1 or T2 (see definitions above) that is compatible with
program/project objectives. You can obtain a plot of the corresponding labor hours
(months), K1 or K2 (see definitions above) spread over the selected period of time by
going to the COSYSMORLABSCHED page of the COSYSMOR tool and enter the
amount of labor in cell Q91, first putting an”X” in cell O91, indicating “Self-Select”
value of labor and the length of the schedule in cell T99, first putting an “X” in cell R91
to indicate “Self-Select” value of schedule.
The SCHEDESTSE tool function also provides a tabulation and a plot of effort, K as a
function of T, schedule. Further, it provides a tabulation and a plot of percent change of
effort, K2/K1, as a function of percent change of schedule, T2/T1. You can use the data in
the tables and the plots to provide you some insight into the relationship between
schedule and effort and the possible affect on effort of changing the project scheduler.
Examples of the Tables and plots are provided below.
The figure below shows the Schedule/Effort Relationship Estimator tool found on the
COSYSMOR SCHEDESTSEUSER tool page.
3
Systems Engineering Schedule/Effort Relationship Estimator,SCHEDESTSE
1. Enter calendar Weeks per Month that you wish to use to transform a schedule given in
months to one given in weeks.
Weeks per Month
4.3
2. Estimate baseline schedule. Typically, this is one corresponding to one of effort values in
the range of such values that you estimated using COSYSMOR. Enter Person Hours value
and Size,Equivalent Requirements value and the tool provides the corresponding schedule.
Equiv Reqmts Person Hours
Schedule (Months)
1203
46957
Processing In Box
Schedule (Weeks)
48.0
Unit Effort (PHrs /EReq)
206
Productivity (EReq/100 PHrs)
39.0
2.6
1.6809
3. Decide if the schedule value calculated above is satisfactory. If so,go to step 5.
Else, if it is not satisfactory, go to step 4.
4. If you desire a different ("better") schedule, enter the desired value here, and obtain the corresponding
person hours estimate. It is suggested that the "better" schedule be within the range of +/-50% that of
the baseline schedule, K1 in the table below, that was calculated in Step 2 above.
Base estimated schedule, T1=
Better schedule, T 2=
And, given that K 1=
48.0 Months
206 Weeks
50.0 Months
215 Weeks
46957 Person Hours
Therefore, corresponding effort, K2=
46791 Person Hours
Therefore, T2/T1=
104.25%
Therefore, K2/K1=
99.65%
Tables SCHEDEST 1 & 2, below, tabulate K2/K1 % as a function of T 2/T1 % over the range 50% to 150% and also
K, Effort (Person Hours) as a function of T,Schedule (Months). The two Tables are plotted on
page SCHEDESTSEPLOTS.
Table SCHEDEST 1
Table SCHEDEST 2
For Baseline Effort = 46957
T2/T1
K2/K1
and Schedule= 48.0
50.00%
106.07%
60.00%
104.44%
T, Schedule (Months)
24.0
K, Effort (Person hours)
49808
70.00%
103.08%
28.8
49042
80.00%
101.92%
33.6
48403
90.00%
100.90%
38.4
47857
100.00%
100.00%
43.2
47380
110.00%
99.19%
48.0
46957
120.00%
98.46%
52.8
46578
130.00%
97.79%
57.6
46235
140.00%
97.18%
62.3
45921
150.00%
96.61%
67.1
45632
71.9
45366
5. If you desire to spread the person hours estimate over the schedule estimate (period of time)
obtained in step 2 or step 4, then go to the COSYSMORLABSCHED page and do the following:
amount of labor in cell Q91, first putting an”X” in cell O91, indicating “Self-Select” value of
labor and the length of the schedule in cell T99, first putting an “X” in cell R91 to indicate
the “Self-Select” value of schedule.
4
% Systems Engineering Effort Change,K2/K1
Versus % Schedue Change,T2/T1
K2/K1 Percent
108%
106%
104%
102%
100%
98%
96%
50%
60%
70%
80%
90%
100% 110%
120%
130%
140%
150%
T2/T1 Percent
K, Effort (Systems Engineering Person Hours)
Versus T, Schedule (Months), For Baseline K and
T 46957 and 48.0
K, Person Hours
51000
50000
49000
48000
47000
46000
45000
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
T, Months
5