Fixed-size and fixed-duration moving windows were evaluated with estimation by analogy (EbA) effort estimation. With fixed-size windows, the modified EbA showed moving windows became significantly advantageous over the growing portfolio at medium window sizes, while trends were similar but ranges differed from past studies. With fixed-duration windows, moving windows improved accuracy less significantly than fixed-size windows over smaller window sizes. Comparisons with past studies found overall trends the same but effective window sizes and ranges differed.

1. The
Effects
of
Duration-­‐based
Moving
Windows
with
Estimation
by
Analogy
Sousuke
Amasaki*
Chris
Lokan†
Okayama
Prefectural
University*
UNSW
Canberra†
Mensura
2015
in
Kracow,
Poland
1

2. In
Mensura
2012,
we
focused
on
Moving
Windows
for
Effort
Estimation
with
Estimation
by
Analogy
2
Mensura
2015
in
Kracow,
Poland
Project Data for Training
EbA Effort Estimation Model
A target project
to be estimated
Drop off old
project,
it maybe useless
Retain
Window Size
A new target
past
future
Conclusion in Mensura 2012 paper
• MW could improve accuracy with EbA
• Weaker effects with EbA than Linear Regression

3. Window
policies
matter
3
p MW
was
examined
with
LR
and
two
policies
[IST2014]*
p Fixed-­‐size
p Retain
N
projects
in
a
window
p Fixed-­‐duration
p Retain
projects
within
N
months
p Results
show
the
difference
in
accuracy
improvement
*
C.
Lokan,
E.
Mendes.
Investigating
the
use
of
duration-­‐based
moving
windows
to
improve
software
effort
prediction:
A
replicated
study,
Information
and
Software
Technology
56(9)
,
pp.
1063–1075,
2014.
Mensura
2015
in
Kracow,
Poland

4. Today’s
talk
is
about
Duration-­‐based
Moving
Windows
4
Mensura
2015
in
Kracow,
Poland
past
future
Fixed-size (Mensura 2012)
Fixed-duration
EbA with pre-selected
features (Mensura 2012)
EbA with on-time feature
selection (for reality)

5. Research
Questions
5
Mensura
2015
in
Kracow,
Poland
Is
there
a
difference
in
the
accuracy
of
estimates
between
EbA
with
pre-­‐
and
on-­‐time
selections
using
fixed-­‐size
windows?
RQ1. Reconfirmation of Mensura 2012 results
Is
there
a
difference
in
the
accuracy
of
estimates
with
and
without
MW
with
the
revised
EbA
and
fixed
duration
windows?
RQ2. Evaluation of Fixed-Duration Windows
RQ3. Comparison between window policies
How
do
these
results
compare
with
results
based
on
fixed-­‐size
windows?

6. The
revised
EbA
Mensura
2015
in
Kracow,
Poland
6
p Select
features
on
the
basis
of
the
whole
dataset
p Wrapper
approach
p Use
simple
mean
for
estimation
Mensura 2012
p Select
features
for
every
new
target
project
p Lasso
for
reducing
computation
costs
p Use
inverse
rank
weighted
mean
(IRWM)
for
estimation
This study
Unrealistic to use
future projects
Contribute to
estimation accuracy

7. Dataset
Mensura
2015
in
Kracow,
Poland
7
Properties
p Highly quality rated as A or B by ISBSG
p Size Measured with IFPUG 4.0 or later
p Known Actual effort
p Not web projects
p 228 projects
Candidate predictors
p Unadjusted FP
p Language types
p Development types
p Platform types
p Domain Sector types
As same as Mensura 2012

8. Experiments
Mensura
2015
in
Kracow,
Poland
8
p Mensura
2012
EbA
vs.
the
revised
EbA
(for
RQ1)
p Growing
Portfolio
(use
all
past
projects)
vs.
Moving
Windows
(for
RQ2,
RQ3)
Performance
trend
analysis
Preference
Preference
Statistical
significance
Statistical
significance
Comparisons
between:
p From
12
to
84
months
(fixed-­‐duration)
p From
20
to
120
projects
(fixed-­‐size)

9. Results:
fixed-­‐size
windows
with
the
revised
EbA
Mensura
2015
in
Kracow,
Poland
9
8 Sousuke Amasaki and Chris Lokan
20 40 60 80 100 120
Window Size (number of projects)
10
5
0
5
DifferencesinmeanAE(%)
(a) Di↵erences in mean MAE
8 Sousuke Amasaki and Chris Lokan
(a) Di↵erences in mean MAE
20 40 60 80 100 120
Window Size (number of projects)
15
10
5
0
5
10
DifferencesinmeanMRE(%) (b) Di↵erences in mean MRE
Fig. 1: Results with Fixed-size Window, modified EbA with k = 5
Figure 1 and Table 2 revealed characteristics of moving windows compared
to the growing portfolio:
– With windows of up to 60 projects, MAE showed no significant preference
for any approach. The line starts below zero and quickly goes above zero
(favoring the growing portfolio), but the di↵erence was not significant as shown
p GP was advantageous in smaller window sizes but not significant
p MW got significantly advantageous in medium window size
Num of Neighbors k = 5

10. Results:
comparisons
between
the
old
and
the
revised
EbA
Mensura
2015
in
Kracow,
Poland
10
8 Sousuke Amasaki and Chris Lokan
20 40 60 80 100 120
Window Size (number of projects)
10
5
0
5
DifferencesinmeanAE(%)
(a) Di↵erences in mean MAE
8 Sousuke Amasaki and Chris Lokan
(a) Di↵erences in mean MAE
20 40 60 80 100 120
Window Size (number of projects)
15
10
5
0
5
10
DifferencesinmeanMRE(%)
(b) Di↵erences in mean MRE
Fig. 1: Results with Fixed-size Window, modified EbA with k = 5
Figure 1 and Table 2 revealed characteristics of moving windows compared
to the growing portfolio:
– With windows of up to 60 projects, MAE showed no significant preference
for any approach. The line starts below zero and quickly goes above zero
(favoring the growing portfolio), but the di↵erence was not significant as shown
Num of Neighbors k = 5
p Trends were same but effective sizes and ranges were differentp Trends were same but effective sizes and ranges were different
p The best k moved from k=2 (Mensura 2012) to k=5
p Trends were same but effective sizes and ranges were different
p The best k moved from k=2 (Mensura 2012) to k=5
p The improvement by MW was clearer in statistical significance

11. Results:
fixed-­‐duration
windows
with
the
revised
EbA
Mensura
2015
in
Kracow,
Poland
11
12 Sousuke Amasaki and Chris Lokan
20 30 40 50 60 70 80
Window Size (calendar months)
10
5
0
5
DifferencesinmeanAE(%)
(a) Di↵erences in mean MAE
(a) Di↵erences in mean MAE
20 30 40 50 60 70 80
Window Size (calendar months)
15
10
5
0
5
DifferencesinmeanMRE(%)
(b) Di↵erences in mean MRE
Fig. 2: Results with Fixed-duration Windows, EbA with k = 5
growing portfolio are larger with EbA than with LR, and the range of durations
for which windows are advantageous is narrower with EbA than with LR. The
di↵erence in advantageous window sizes and their number between EbA and
LR were reported in [4]. These observations were common between this study
and [4].
p GP was advantageous in smaller window sizes but not significant
p MW got significantly advantageous in medium window size
p Less significant window sizes than fixed-size windows
Num of Neighbors k = 5

12. Results:
comparison
to
the
past
study
[IST2014]
Mensura
2015
in
Kracow,
Poland
12
12 Sousuke Amasaki and Chris Lokan
20 30 40 50 60 70 80
Window Size (calendar months)
10
5
0
5
DifferencesinmeanAE(%)
(a) Di↵erences in mean MAE
(a) Di↵erences in mean MAE
20 30 40 50 60 70 80
Window Size (calendar months)
15
10
5
0
5
DifferencesinmeanMRE(%)
(b) Di↵erences in mean MRE
Fig. 2: Results with Fixed-duration Windows, EbA with k = 5
growing portfolio are larger with EbA than with LR, and the range of durations
for which windows are advantageous is narrower with EbA than with LR. The
di↵erence in advantageous window sizes and their number between EbA and
LR were reported in [4]. These observations were common between this study
and [4].
Num of Neighbors k = 5
p Overall trend was same between the two studies
p Fixed-size windows was more effective than fixed-duration
p The effective window size became larger and its range is narrower

13. Answers
to
RQs
13
Mensura
2015
in
Kracow,
Poland
The
change
in
estimation
method
made
a
difference,
improving
the
accuracy
of
estimates.
RQ1. Reconfirmation of Mensura 2012 results
The
fixed-­‐duration
windows
can
make
a
difference,
and
effective
to
improve
estimation
accuracy.
RQ2. Evaluation of Fixed-Duration Windows
RQ3. Comparison between window policies
The
fixed-­‐size
and
fixed-­‐duration
window
policies
can
lead
to
significantly
better
estimation
accuracy.
But
fixed-­‐size
made
clearer
difference.

14. Practical
implications
14
Mensura
2015
in
Kracow,
Poland
This
and
past
studies
showed
its
effectiveness
with
major
effort
estimation
method,
LR
and
EbA.
1. Moving Windows is effective
This
and
past
studies
showed
clearer
difference
when
using
fixed-­‐size
windows.
Rethink
practitioners’
mind
regarding
reference
projects.
2. Fixed-size policy looks better for estimation
3. Effective window sizes might be different even among practitioners
EbA
resembles
practitioners’
thinking.
The
fact
that
the
difference
in
options
resulted
in
different
window
ranges
partly
explain
the
difference
among
practitioners

15. Threats
to
Validity
Mensura
2015
in
Kracow,
Poland
15
p The
result
was
based
on
only
ISBSG
dataset
p It
is
difficult
to
generalize
the
results
Dataset
EbA
p Limited
to
specific
options
p More
accurate
or
more
realistic
settings

16. Conclusion
p Fixed-­‐duration
windows
works
with
EbA
p Under
more
realistic
situation
p The
results
brought
some
practical
implications
p ex.
Fixed-­‐size
policy
is
more
suitable
p Exploration
of
EbA
options
p Additional
experiments
on
other
datasets
16
Mensura
2015
in
Kracow,
Poland
Future Work

17. Mensura
2015
in
Kracow,
Poland
17
We
welcome
questions
!
Sousuke
Amasaki:
amasaki@cse.oka-­‐pu.ac.jp
Chris
Lokan:
c.lokan@adfa.edu.au
Contact
info: